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.Arrays;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Scanner;
  import java.util.Set;
  
  public class Codeforces {
  
  
  	static Scanner sc=new Scanner(System.in);
  
  	public static void main(String[] args) {
  		int t=1;
  		t=sc.nextInt();
  
  		while(t-->0) {
  			solve();
  		}
  
  	}
  
  	private static void solve() {
  
  
  		
  		int n=sc.nextInt();
  		long arr[]=new long[n];
  		for(int i=0;i<n;i++) {
  			arr[i]=sc.nextLong();
  		}
  		Arrays.sort(arr);
  		
  		long leftSum[]=new long[n];
  		long rightSum[]=new long[n];
  		
  		leftSum[0]=arr[0];
  		for(int i=1;i<n;i++) {
  			leftSum[i]=leftSum[i-1]+arr[i];
  		}
  		rightSum[n-1]=arr[n-1];
  		for(int i=n-2;i>=0;i--) {
  			rightSum[i]=rightSum[i+1]+arr[i];
  		}
  		double tSum=Integer.MIN_VALUE;
  		//System.out.println(tSum);
  		
  		for(int i=1;i<n;i++) {
  			double sum= ((leftSum[i-1]*1.0)/i)+((rightSum[i]*1.0)/(n-i));
  			//System.out.println(sum);
  			if(sum>tSum) {
  				tSum=sum;
  			}
  		}
  		
  		System.out.printf("%.9f", tSum);
  		System.out.println();
  		
  		//System.out.println(tSum);
  		
  		/*int n=sc.nextInt(),k=sc.nextInt();
  		long[] ar=new long[n];
  		for(int i=0;i<n;i++) {
  			ar[i]=sc.nextLong();
  		}
  		long[] st=Arrays.copyOf(ar,n);
  		HashMap<Long,Integer> hm=new HashMap<Long,Integer>();
  		Arrays.sort(st);
  
  		for(int i=0;i<n;i++)
  			hm.put(st[i],i);
  
  		int sub=0,ind=-1;
  		for(int i=0;i<n;i++){
  			sub++;
  			ind=hm.get(ar[i]);
  			while(st[ind]==ar[i]){
  				i++;
  				ind++;
  				if(i==n||ind==n||st[ind]!=ar[i]){
  					i--;
  					break;
  				}
  			}
  		}
  
  		if(k>=sub) System.out.println("YES");
  		else System.out.println("NO");
  
  		/*int n=sc.nextInt();
  		int k=sc.nextInt();
  
  		Map<Long, Integer> map=new HashMap<>();
  
  		for(int i=0;i<n;i++) {
  			long val=sc.nextLong();
  			map.put(val, i);
  		}
  		int arr[]=new int[n];
  		Set<Long> set=map.keySet();
  		int j=0;
  		for(Long i:set) {
  			arr[j++]=map.get(i);
  		}
  
  		int l=1;
  		for(int i=1;i<n;i++) {
  			if(arr[i]-arr[i-1]!=1) {
  				l++;
  			}
  		}
  		if(l<=k) {
  			System.out.println("YES");
  		}else {
  			System.out.println("NO");
  		}
  
  
  		/*long n=sc.nextLong();
  		long x=sc.nextLong();
  		long t=sc.nextLong();
  
  		long disFor1=t/x;
  		if(disFor1>n) {
  			System.out.println((n*(n-1)/2));
  			return;
  		}
  
  		long tDis=(n-disFor1)*disFor1;
  		tDis+=(disFor1*(disFor1-1))/2;
  		System.out.println(tDis);
  
  
  
  		/*
  		String s=sc.next();
  		int aScore=0;
  		int a2=0;
  		int bScore=0;
  		int b2=0;
  
  		for(int i=0;i<s.length();i++) {
  			if(i%2==0) {
  				if(s.charAt(i)=='1') {
  					aScore++;
  				}else if(s.charAt(i)=='?'){
  					a2++;
  				}
  
  
  
  
  			}else {
  				if(s.charAt(i)=='1') {
  					bScore++;
  				}else if(s.charAt(i)=='?'){
  					b2++;
  				}
  
  
  
  			}
  			int bRem=5-((i+1)/2);
  			if(aScore+a2-bScore>bRem) {
  				System.out.println(i+1);
  				return;
  			}
  			int aRem=5-(i/2+1);
  			if(bScore+b2-aScore>aRem) {
  				System.out.println(i+1);
  				return;
  			}
  
  		}
  		System.out.println(10);
  
  		/*
  		int n=sc.nextInt();
  		long arr[]=new long[n];
  		for(int i=0;i<n;i++) {
  			arr[i]=sc.nextLong();
  		}
  		long l1=Integer.MIN_VALUE;
  		long l2=Integer.MIN_VALUE;
  		int index1=0;
  		int index2=0;
  		for(int i=0;i<n;i++) {
  			if(arr[i]>l1) {
  				l2=l1;
  				l1=arr[i];
  				index2=index1;
  				index1=i;
  
  			}else if(arr[i]>l2 && arr[i]!= l1) {
  				l2=arr[i];
  				index2=i;
  			}
  
  		}
  		System.out.println(index2+1);
  
  		/*
  		int a=sc.nextInt();
  		int b=sc.nextInt();
  		int c=a^b;
  		System.out.println(c);
  
  		/*long a=sc.nextLong();
  		long b=sc.nextLong();
  
  		if(a==b) {
  			System.out.println(0+" "+0);
  			return;
  		}
  
  		long gcd=Math.abs(a-b);
  
  		long rem=a%gcd;
  
  		long min=Math.min(rem, gcd-rem);
  		System.out.println(gcd+" "+min);
  
  
  
  		/*int n=sc.nextInt();
  		long arr[]=new long[n];
  
  		long sum=0;
  		for(int i=0;i<n;i++) {
  			arr[i]=sc.nextInt();
  			sum+=arr[i];
  		}
  
  		long rem=sum%n;
  
  		long ans=rem*(n-rem);
  		System.out.println(ans);
  		 */
  	}
  
  }
  