#include<cstdio>#include<algorithm>#include<cstring>#include<string>#include<iostream>#define maxn 110using namespace std;int dp[maxn][maxn];int vis[maxn][maxn];int num[maxn];int sum[maxn];bool cmp(int a,int b){    return a>b;}int get(int a,int b){//    printf("%d %d---\n",a,b);    if(vis[a][b])return dp[a][b];    int& ans=dp[a][b];    ans=999999999;    vis[a][b]=1;    for(int i=b-1; i<a; i++)    {        ans=min(ans,get(i,b-1)+(sum[a]-sum[i])*a);    }    return ans;}int main(){    int t,n,w;    scanf("%d",&t);    while(t--)    {        scanf("%d%d",&n,&w);        int all=0;        for(int i=1; i<=n; i++)        {            scanf("%d",&num[i]);            all+=num[i];        }        sort(num+1,num+n+1,cmp);        for(int i=1; i<=n; i++)            sum[i]=sum[i-1]+num[i];        memset(vis,0,sizeof vis);        for(int i=1; i<=n; i++)        {            vis[i][i]=1;            dp[i][i]=dp[i-1][i-1]+num[i]*i;            vis[i][1]=1;            dp[i][1]=sum[i]*i;        }        int ans=get(n,w);        printf("%.4lf\n",((double)ans/(double)all));    }    return 0;}