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.util.*;
  import java.io.*;
  
  public class temp {
  
      public static void main(String[] args) {
          JS scan = new JS();
          int t = scan.nextInt();
          for (int q = 1; q <= t; q++) {
              int n = scan.nextInt();
  
              long sum = 0;
              long max = Long.MIN_VALUE;
  
              for(int i = 0; i < n; i++) {
                  long x = scan.nextLong();
                  sum += x;
                  max = Math.max(max, x);
              }
  
              double first = max;
              double second = sum - max;
              second /= (n-1);
  
              System.out.println(first+second);
          }
      }
  
      static class JS {
          public int BS = 1<<16;
          public char NC = (char)0;
          byte[] buf = new byte[BS];
          int bId = 0, size = 0;
          char c = NC;
          double num = 1;
          BufferedInputStream in;
  
          public JS() {
              in = new BufferedInputStream(System.in, BS);
          }
  
          public JS(String s) throws FileNotFoundException {
              in = new BufferedInputStream(new FileInputStream(new File(s)), BS);
          }
  
          public char nextChar(){
              while(bId==size) {
                  try {
                      size = in.read(buf);
                  }catch(Exception e) {
                      return NC;
                  }
                  if(size==-1)return NC;
                  bId=0;
              }
              return (char)buf[bId++];
          }
  
          public int nextInt() {
              return (int)nextLong();
          }
  
          public long nextLong() {
              num=1;
              boolean neg = false;
              if(c==NC)c=nextChar();
              for(;(c<'0' || c>'9'); c = nextChar()) {
                  if(c=='-')neg=true;
              }
              long res = 0;
              for(; c>='0' && c <='9'; c=nextChar()) {
                  res = (res<<3)+(res<<1)+c-'0';
                  num*=10;
              }
              return neg?-res:res;
          }
  
          public double nextDouble() {
              double cur = nextLong();
              return c!='.' ? cur:cur+(cur < 0 ? -1*nextLong()/num : nextLong()/num);
          }
  
          public String next() {
              StringBuilder res = new StringBuilder();
              while(c<=32)c=nextChar();
              while(c>32) {
                  res.append(c);
                  c=nextChar();
              }
              return res.toString();
          }
      }
  }