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.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.StringTokenizer;
  
  public class Solver {
  
      public static void main(String[] args) {
          FastReader in = new FastReader();
          PrintWriter out = new PrintWriter(System.out);
          new TaskA().solveA(in, out);
          out.close();
      }
  
      static class TaskA {
          public void solveA(FastReader in, PrintWriter out) {
              int t = in.nextInt();
  
              while (t-- > 0) {
                  int n = in.nextInt();
                  long[] array = in.nextLongArray(n);
                  double[] sumArray = new double[n];
                  Arrays.sort(array);
                  sumArray[0] = array[0];
                  for (int i = 1; i < n; i++) {
                      sumArray[i] = sumArray[i - 1] + array[i];
                  }
  
                  double result = -90000000000.0;
                  for (int i = 0; i < n - 1; i++) {
                      double temp = (sumArray[i] / (i + 1)) + (sumArray[n - 1] - sumArray[i]) / (n - i - 1);
                      result = result > temp ? result : temp;
                  }
  
                  out.println(String.format("%.6f", result));
              }
          }
  
          public void solveB(FastReader in, PrintWriter out) {
  
          }
  
          public void solveC(FastReader in, PrintWriter out) {
  
          }
  
          public void solveD(FastReader in, PrintWriter out) {
  
          }
  
          public void solveE(FastReader in, PrintWriter out) {
  
          }
      }
  
      private static long gcd(long a, long b) {
          if (a == 0) {
              return b;
          }
          return gcd(b % a, a);
      }
  
      private static long lcm(long a, long b) {
          return (a * b) / gcd(a, b);
      }
  
      private static int min(int a, int b) {
          return a < b ? a : b;
      }
  
      private static int max(int a, int b) {
          return a > b ? a : b;
      }
  
      private static int min(ArrayList<Integer> list) {
          int min = Integer.MAX_VALUE;
          for (int el : list) {
              if (el < min) {
                  min = el;
              }
          }
          return min;
      }
  
      private static int max(ArrayList<Integer> list) {
          int max = Integer.MIN_VALUE;
          for (int el : list) {
              if (el > max) {
                  max = el;
              }
          }
          return max;
      }
  
      private static int min(int[] list) {
          int min = Integer.MAX_VALUE;
          for (int el : list) {
              if (el < min) {
                  min = el;
              }
          }
          return min;
      }
  
      private static int max(int[] list) {
          int max = Integer.MIN_VALUE;
          for (int el : list) {
              if (el > max) {
                  max = el;
              }
          }
          return max;
      }
  
      private static void fill(int[] array, int value) {
          for (int i = 0; i < array.length; i++) {
              array[i] = value;
          }
      }
  
      static class FastReader {
          BufferedReader br;
          StringTokenizer st;
  
          public FastReader() {
              br = new BufferedReader(new InputStreamReader(System.in));
          }
  
          String next() {
              while (st == null || !st.hasMoreElements()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
  
          int nextInt() {
              return Integer.parseInt(next());
          }
  
          long nextLong() {
              return Long.parseLong(next());
          }
  
          double nextDouble() {
              return Double.parseDouble(next());
          }
  
          String nextLine() {
              String str = "";
              try {
                  str = br.readLine();
              } catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
  
          int[] nextIntArray(int n) {
              int[] array = new int[n];
              for (int i = 0; i < n; i++) {
                  array[i] = nextInt();
              }
              return array;
          }
  
          long[] nextLongArray(int n) {
              long[] array = new long[n];
              for (int i = 0; i < n; i++) {
                  array[i] = nextLong();
              }
              return array;
          }
      }
  }