#include<stdio.h>
int main()
{
    int c;
    scanf("%d",&c);
    int i;
    float answer[c+1];
    float L[c+1],N[c+1];
    for(i=1; i<=c; i++)
    {
        scanf("%f %f",&L[i],&N[i]);
        float average,best=100;
        int j;
        float rent[c+1],sum=0;
        for(j=1; j<=L[i]; j++)
            scanf("%f",&rent[j]);
        while(L[i]>=N[i])
        {
            for(j=1; j<N[i]; j++)
                sum+=rent[j];
            for(j=N
            [i]; j<=L[i]; j++)
            {
                sum+=rent[j];
                average=sum/(N[i]);
                if(best>average)
                    best=average;
                sum-=rent[j-int(N[i])+1];
            }
             N[i]++;
             sum=0;

        }
        answer[i]=best;
    }
    for(i=1;i<=c;i++)
        printf("%.10f\n",answer[i]);
}