#include<bits/stdc++.h>

using namespace std;

const int maxn = 100+;

int u[maxn];

int f[][maxn];

const int INF = 0x3f3f3f3f;

//#define LOCAL

int main()

{

#ifdef LOCAL

    freopen("in.txt","r",stdin);

#endif

    int T; cin>>T;

    while(T--){

        int n,w; scanf("%d%d",&n,&w);

        for(int i = ; i <= n; i++) scanf("%d",u+i);

        sort(u+,u++n,greater<int>());

        for(int i = ; i <= n; i++) u[i] += u[i-];

        for(int j = n; j > ; j--){

            f[][j] = (n-j+)*(u[n]-u[j-]);

        }

        for(int i = ; i <= w; i++){

            for(int j = ; j <= n; j++){

                f[i][j] = INF;

                for(int k = j+; k <= n; k++){

                    f[i][j] = min(f[i-][k]+(k-j)*(u[n]-u[j-]),f[i][j]);

                }

            }

        }

        printf("%.4lf\n", f[w][]/(double)u[n]);

    }

    return ;

}