#include <stdio.h>

int main()
{
    int C, N, L, tmp_L, sum = 0;
    int day[1000];
    double min = 100000000000.0;
    double avg = 0.0;

    fscanf(stdin, "%d", &C);

    while (C--){
        fscanf(stdin, "%d %d", &N, &L);
        for (int i = 0; i < N; i++)
            fscanf(stdin, "%d", &day[i]);

        tmp_L = L;
        while (tmp_L != N){
            for (int i = 0; i + tmp_L <= N; i++) {
                sum = 0;

                for (int j = i; j < i + tmp_L; j++) {
                    sum += day[j];
                }

                avg = (double)sum / tmp_L;
                if (min > avg)
                    min = avg;
            }
            tmp_L++;
        }
        fprintf(stdout, "%.12f\n", min);
    }
    return 0;

}