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.*;
  import java.util.*;
  
  public class Codeforces {
      public static void main(String[] args) throws IOException {
          FastScanner fs = new FastScanner();
          PrintWriter pw = new PrintWriter(System.out);
          int t = 1;
          t = fs.getInt();
          while (t-- > 0) {
              int n = fs.getInt();
              int[] ar = fs.getIntArray(n);
              Utility.sort(ar);
              double s1 = ar[0] + 0.0;
              double c1 = 1;
  
              double s2 = ar[n - 1];
              double c2 = 1;
  
              for (int i = 1; i < n - 1; i++) {
                  double k1 = (s1 + ar[i]) / (c1 + 1) + s2 / c2;
                  double k2 = (s2 + ar[i]) / (c2 + 1) + s1 / c1;
                  if (k1 > k2) {
                      s1 += ar[i];
                      c1++;
                  } else {
                      s2 += ar[i];
                      c2++;
                  }
              }
              pw.println((s1 / c1) + (s2 / c2));
          }
          pw.close();
      }
  
      static boolean arraySortedOrNot(int ar[], int n) {
          if (n == 0 || n == 1)
              return true;
  
          for (int i = 1; i < n; i++)
  
              if (ar[i - 1] > ar[i])
                  return false;
  
          return true;
      }
  
  }
  
  class MOD {
      static long mod = 1000000007;
  
      static long add(long x, long y) {
          return (x % mod + y % mod) % mod;
      }
  
      static long sub(long x, long y) {
          return (x % mod - y % mod) % mod;
      }
  
      static long mul(long x, long y) {
          return (x % mod * y % mod) % mod;
      }
  
      static long pow(long x, long y) {
          long result = 1;
          x %= mod;
          while (y > 0) {
              if ((y & 1) == 1)
                  result = mul(result, x);
              x = mul(x, x);
              y = y >>> 1;
          }
          return result;
      }
  
      static long modInv(long x) {
          return pow(x, mod - 2);
      }
  
  }
  
  class Utility {
      static int ceil(int a, int b) {
          if (a == 0)
              return 0;
          return (a - 1) / b + 1;
      }
  
      static long ceil(long a, long b) {
          if (a == 0)
              return 0;
          return (a - 1) / b + 1;
      }
  
      static int gcd(int a, int b) {
          if (a > b) {
              int t = a;
              a = b;
              b = t;
          }
          if (a == 0)
              return b;
          return gcd(b % a, a);
      }
  
      static long gcd(long a, long b) {
          if (a > b) {
              long t = a;
              a = b;
              b = t;
          }
          if (a == 0)
              return b;
          return gcd(b % a, a);
      }
  
      static int binarySearch(int[] ar, int x, int start, int end) {
          int l = start;
          int r = end;
          while (l <= r) {
              int mid = l + (r - l) / 2;
              if (ar[mid] == x) {
                  return mid;
              } else if (ar[mid] > x) {
                  r = mid - 1;
              } else {
                  l = mid + 1;
              }
          }
          return -1;
      }
  
      static int lowerBound(int[] ar, int x) {
          int l = 0;
          int r = ar.length - 1;
          while (l <= r) {
              int mid = l + (r - l) / 2;
  
              if (ar[mid] >= x)
                  r = mid - 1;
              else
                  l = mid + 1;
          }
          return r + 1;
      }
  
      static int upperBound(int[] ar, int x) {
          int l = 0;
          int r = ar.length - 1;
          while (l <= r) {
              int mid = l + (r - l) / 2;
  
              if (ar[mid] > x)
                  r = mid - 1;
              else
                  l = mid + 1;
          }
          return l;
      }
  
      static void sort(int[] ar) {
          ArrayList<Integer> l = new ArrayList<>();
          for (int i : ar)
              l.add(i);
          Collections.sort(l);
          for (int i = 0; i < ar.length; i++)
              ar[i] = l.get(i);
      }
  
      static void sortReverse(int[] ar) {
          ArrayList<Integer> l = new ArrayList<>();
          for (int i : ar)
              l.add(i);
          Collections.sort(l, Collections.reverseOrder());
          for (int i = 0; i < ar.length; i++)
              ar[i] = l.get(i);
      }
  
      static void sort(long[] ar) {
          ArrayList<Long> l = new ArrayList<>();
          for (long i : ar)
              l.add(i);
          Collections.sort(l);
          for (int i = 0; i < ar.length; i++)
              ar[i] = l.get(i);
      }
  
      static void sortReverse(long[] ar) {
          ArrayList<Long> l = new ArrayList<>();
          for (long i : ar)
              l.add(i);
          Collections.sort(l, Collections.reverseOrder());
          for (int i = 0; i < ar.length; i++)
              ar[i] = l.get(i);
      }
  
      static void printArray(int[] ar, PrintWriter pw) {
          for (int i = 0; i < ar.length; i++) {
              pw.print(ar[i] + " ");
          }
          pw.println();
      }
  
      static void printArray(long[] ar, PrintWriter pw) {
          for (int i = 0; i < ar.length; i++) {
              pw.print(ar[i] + " ");
          }
          pw.println();
      }
  
      static void printIntList(List<Integer> list, PrintWriter pw) {
          for (int i = 0; i < list.size(); i++) {
              pw.print(list.get(i) + " ");
          }
          pw.println();
      }
  
      static void printLongList(List<Long> list, PrintWriter pw) {
          for (int i = 0; i < list.size(); i++) {
              pw.print(list.get(i) + " ");
          }
          pw.println();
      }
  
      static long choose(long n, long k) {
          long res = 1;
          if (k > n - k)
              k = n - k;
          for (long i = 0; i < k; i++) {
              res *= (n - i);
              res /= (i + 1);
          }
          return res;
      }
  }
  
  class Pair implements Comparable<Pair> {
      Integer first;
      Integer second;
  
      Pair(Integer f, Integer s) {
          this.first = f;
          this.second = s;
      }
  
      public String toString() {
          return "(" + this.first + ", " + this.second + ")";
      }
  
      @Override
      public boolean equals(Object object) {
          if (((Pair) object).first == this.first && ((Pair) object).second == this.second && object instanceof Pair) {
              return true;
          } else {
              return false;
          }
      }
  
      @Override
      public int hashCode() {
          return (String.valueOf(first) + ":" + String.valueOf(second)).hashCode();
      }
  
      @Override
      public int compareTo(Pair p) {
          int f = first.compareTo(p.first);
          if (f != 0)
              return f;
  
          return Integer.compare(second, p.second);
      }
  }
  
  class FastScanner {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st = new StringTokenizer("");
  
      String next() {
          while (!st.hasMoreTokens())
              try {
                  st = new StringTokenizer(br.readLine());
              } catch (IOException e) {
                  e.printStackTrace();
              }
          return st.nextToken();
      }
  
      int getInt() {
          return Integer.parseInt(next());
      }
  
      long getLong() {
          return Long.parseLong(next());
      }
  
      int[] getIntArray(int n) {
          int[] a = new int[n];
          for (int i = 0; i < n; i++)
              a[i] = getInt();
          return a;
      }
  
      long[] getLongArray(int n) {
          long[] a = new long[n];
          for (int i = 0; i < n; i++)
              a[i] = getLong();
          return a;
      }
  
      List<Integer> getIntList(int n) {
          List<Integer> list = new ArrayList<>();
          for (int i = 0; i < n; i++)
              list.add(getInt());
          return list;
      }
  
      List<Long> getLongList(int n) {
          List<Long> list = new ArrayList<>();
          for (int i = 0; i < n; i++)
              list.add(getLong());
          return list;
      }
  }
  