description: Ezzat has an array of n integers (maybe negative). He wants to split it into two non-empty subsequences a and b, such that every element from the array belongs to exactly one subsequence, and the value of f(a) + f(b) is the maximum possible value, where f(x) is the average of the subsequence x. 
  
  A sequence x is a subsequence of a sequence y if x can be obtained from y by deletion of several (possibly, zero or all) elements.
  
  The average of a subsequence is the sum of the numbers of this subsequence divided by the size of the subsequence.
  
  For example, the average of [1,5,6] is (1+5+6)/3 = 12/3 = 4, so f([1,5,6]) = 4.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10^3)— the number of test cases. Each test case consists of two lines.
  
  The first line contains a single integer n (2 ≤ n ≤ 10^5).
  
  The second line contains n integers a_1, a_2, …, a_n (-10^9 ≤ a_i ≤ 10^9).
  
  It is guaranteed that the sum of n over all test cases does not exceed 3⋅10^5.
  
  Output
  
  For each test case, print a single value — the maximum value that Ezzat can achieve.
  
  Your answer is considered correct if its absolute or relative error does not exceed 10^{-6}.
  
  Formally, let your answer be a, and the jury's answer be b. Your answer is accepted if and only if \frac{|a - b|}{max{(1, |b|)}} ≤ 10^{-6}.
  
  Example
  
  Input
  
  
  4
  3
  3 1 2
  3
  -7 -6 -6
  3
  2 2 2
  4
  17 3 5 -3
  
  
  Output
  
  
  4.500000000
  -12.500000000
  4.000000000
  18.666666667
  
  Note
  
  In the first test case, the array is [3, 1, 2]. These are all the possible ways to split this array: 
  
    * a = [3], b = [1,2], so the value of f(a) + f(b) = 3 + 1.5 = 4.5. 
    * a = [3,1], b = [2], so the value of f(a) + f(b) = 2 + 2 = 4. 
    * a = [3,2], b = [1], so the value of f(a) + f(b) = 2.5 + 1 = 3.5. 
  
  Therefore, the maximum possible value 4.5.
  
  In the second test case, the array is [-7, -6, -6]. These are all the possible ways to split this array: 
  
    * a = [-7], b = [-6,-6], so the value of f(a) + f(b) = (-7) + (-6) = -13. 
    * a = [-7,-6], b = [-6], so the value of f(a) + f(b) = (-6.5) + (-6) = -12.5. 
  
  Therefore, the maximum possible value -12.5.
solution: import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.io.PrintWriter;
  import java.math.BigInteger;
  import java.util.*;
  
  /**
   * @author Mubtasim Shahriar
   */
  
  public class Cr737 {
  
      public static void main(String[] args) {
  
          InputStream inputStream = System.in;
          OutputStream outputStream = System.out;
          InputReader sc = new InputReader(inputStream);
          PrintWriter out = new PrintWriter(outputStream);
          Solver solver = new Solver();
  		int t = sc.nextInt();
  //        int t = 1;
          while (t-- != 0) {
              solver.solve(sc, out);
          }
          out.close();
  
      }
  
      static class Solver {
          public void solve(InputReader sc, PrintWriter out) {
              int n = sc.nextInt();
              long[] arr = sc.nextLongArray(n);
              sortDec(arr);
              long sum = 0;
              for(long l : arr) sum += l;
              sum -= arr[0];
              out.println((double) arr[0] + (double) sum/(n-1));
          }
  
      }
  
      static void sort(int[] arr) {
          Random rand = new Random();
          int n = arr.length;
          for (int i = 0; i < n; i++) {
              int idx = rand.nextInt(n);
              if (idx == i) continue;
              arr[i] ^= arr[idx];
              arr[idx] ^= arr[i];
              arr[i] ^= arr[idx];
          }
          Arrays.sort(arr);
      }
  
      static void sort(long[] arr) {
          Random rand = new Random();
          int n = arr.length;
          for (int i = 0; i < n; i++) {
              int idx = rand.nextInt(n);
              if (idx == i) continue;
              arr[i] ^= arr[idx];
              arr[idx] ^= arr[i];
              arr[i] ^= arr[idx];
          }
          Arrays.sort(arr);
      }
  
      static void sortDec(int[] arr) {
          Random rand = new Random();
          int n = arr.length;
          for (int i = 0; i < n; i++) {
              int idx = rand.nextInt(n);
              if (idx == i) continue;
              arr[i] ^= arr[idx];
              arr[idx] ^= arr[i];
              arr[i] ^= arr[idx];
          }
          Arrays.sort(arr);
          int l = 0;
          int r = n - 1;
          while (l < r) {
              arr[l] ^= arr[r];
              arr[r] ^= arr[l];
              arr[l] ^= arr[r];
              l++;
              r--;
          }
      }
  
      static void sortDec(long[] arr) {
          Random rand = new Random();
          int n = arr.length;
          for (int i = 0; i < n; i++) {
              int idx = rand.nextInt(n);
              if (idx == i) continue;
              arr[i] ^= arr[idx];
              arr[idx] ^= arr[i];
              arr[i] ^= arr[idx];
          }
          Arrays.sort(arr);
          int l = 0;
          int r = n - 1;
          while (l < r) {
              arr[l] ^= arr[r];
              arr[r] ^= arr[l];
              arr[l] ^= arr[r];
              l++;
              r--;
          }
      }
  
      static class InputReader {
          private boolean finished = false;
  
          private InputStream stream;
          private byte[] buf = new byte[1024];
          private int curChar;
          private int numChars;
          private SpaceCharFilter filter;
  
          public InputReader(InputStream stream) {
              this.stream = stream;
          }
  
          public int read() {
              if (numChars == -1) {
                  throw new InputMismatchException();
              }
              if (curChar >= numChars) {
                  curChar = 0;
                  try {
                      numChars = stream.read(buf);
                  } catch (IOException e) {
                      throw new InputMismatchException();
                  }
                  if (numChars <= 0) {
                      return -1;
                  }
              }
              return buf[curChar++];
          }
  
          public int peek() {
              if (numChars == -1) {
                  return -1;
              }
              if (curChar >= numChars) {
                  curChar = 0;
                  try {
                      numChars = stream.read(buf);
                  } catch (IOException e) {
                      return -1;
                  }
                  if (numChars <= 0) {
                      return -1;
                  }
              }
              return buf[curChar];
          }
  
          public int nextInt() {
              int c = read();
              while (isSpaceChar(c)) {
                  c = read();
              }
              int sgn = 1;
              if (c == '-') {
                  sgn = -1;
                  c = read();
              }
              int res = 0;
              do {
                  if (c < '0' || c > '9') {
                      throw new InputMismatchException();
                  }
                  res *= 10;
                  res += c - '0';
                  c = read();
              } while (!isSpaceChar(c));
              return res * sgn;
          }
  
          public long nextLong() {
              int c = read();
              while (isSpaceChar(c)) {
                  c = read();
              }
              int sgn = 1;
              if (c == '-') {
                  sgn = -1;
                  c = read();
              }
              long res = 0;
              do {
                  if (c < '0' || c > '9') {
                      throw new InputMismatchException();
                  }
                  res *= 10;
                  res += c - '0';
                  c = read();
              } while (!isSpaceChar(c));
              return res * sgn;
          }
  
          public String nextString() {
              int c = read();
              while (isSpaceChar(c)) {
                  c = read();
              }
              StringBuilder res = new StringBuilder();
              do {
                  if (Character.isValidCodePoint(c)) {
                      res.appendCodePoint(c);
                  }
                  c = read();
              } while (!isSpaceChar(c));
              return res.toString();
          }
  
          public boolean isSpaceChar(int c) {
              if (filter != null) {
                  return filter.isSpaceChar(c);
              }
              return isWhitespace(c);
          }
  
          public static boolean isWhitespace(int c) {
              return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
          }
  
          private String readLine0() {
              StringBuilder buf = new StringBuilder();
              int c = read();
              while (c != '\n' && c != -1) {
                  if (c != '\r') {
                      buf.appendCodePoint(c);
                  }
                  c = read();
              }
              return buf.toString();
          }
  
          public String readLine() {
              String s = readLine0();
              while (s.trim().length() == 0) {
                  s = readLine0();
              }
              return s;
          }
  
          public String readLine(boolean ignoreEmptyLines) {
              if (ignoreEmptyLines) {
                  return readLine();
              } else {
                  return readLine0();
              }
          }
  
          public BigInteger readBigInteger() {
              try {
                  return new BigInteger(nextString());
              } catch (NumberFormatException e) {
                  throw new InputMismatchException();
              }
          }
  
          public char nextCharacter() {
              int c = read();
              while (isSpaceChar(c)) {
                  c = read();
              }
              return (char) c;
          }
  
          public double nextDouble() {
              int c = read();
              while (isSpaceChar(c)) {
                  c = read();
              }
              int sgn = 1;
              if (c == '-') {
                  sgn = -1;
                  c = read();
              }
              double res = 0;
              while (!isSpaceChar(c) && c != '.') {
                  if (c == 'e' || c == 'E') {
                      return res * Math.pow(10, nextInt());
                  }
                  if (c < '0' || c > '9') {
                      throw new InputMismatchException();
                  }
                  res *= 10;
                  res += c - '0';
                  c = read();
              }
              if (c == '.') {
                  c = read();
                  double m = 1;
                  while (!isSpaceChar(c)) {
                      if (c == 'e' || c == 'E') {
                          return res * Math.pow(10, nextInt());
                      }
                      if (c < '0' || c > '9') {
                          throw new InputMismatchException();
                      }
                      m /= 10;
                      res += (c - '0') * m;
                      c = read();
                  }
              }
              return res * sgn;
          }
  
          public boolean isExhausted() {
              int value;
              while (isSpaceChar(value = peek()) && value != -1) {
                  read();
              }
              return value == -1;
          }
  
          public String next() {
              return nextString();
          }
  
          public SpaceCharFilter getFilter() {
              return filter;
          }
  
          public void setFilter(SpaceCharFilter filter) {
              this.filter = filter;
          }
  
          public interface SpaceCharFilter {
              public boolean isSpaceChar(int ch);
          }
  
          public int[] nextIntArray(int n) {
              int[] array = new int[n];
              for (int i = 0; i < n; ++i) array[i] = nextInt();
              return array;
          }
  
          public int[] nextSortedIntArray(int n) {
              int array[] = nextIntArray(n);
              Arrays.sort(array);
              return array;
          }
  
          public int[] nextSumIntArray(int n) {
              int[] array = new int[n];
              array[0] = nextInt();
              for (int i = 1; i < n; ++i) array[i] = array[i - 1] + nextInt();
              return array;
          }
  
          public long[] nextLongArray(int n) {
              long[] array = new long[n];
              for (int i = 0; i < n; ++i) array[i] = nextLong();
              return array;
          }
  
          public long[] nextSumLongArray(int n) {
              long[] array = new long[n];
              array[0] = nextInt();
              for (int i = 1; i < n; ++i) array[i] = array[i - 1] + nextInt();
              return array;
          }
  
          public long[] nextSortedLongArray(int n) {
              long array[] = nextLongArray(n);
              Arrays.sort(array);
              return array;
          }
      }
  
  
  }
  