#include<iostream>
using namespace std;
int cost[1001];
int main()
{
    int testcase;
    int N, L;
    double ret;
    int sum;
    double dmin = 100000000.000;
    cin >> testcase;
    while (testcase--)
    {
        cin >> N >> L;
        for (int i = 0; i < N; i++)
            cin >> cost[i];
        while (L <= N)
        {
            for (int i = 0; i < N; i++)
            {
                // L .... N 범위내 최소값구하기
                sum = 0;
                if (i + L > N)
                    break;
                for (int j = i; j < i + L; j++)
                {
                    sum += cost[j];
                }
                ret = sum / (double)L;
                if (dmin > ret)
                    dmin = ret;
            }
            L++;
        }
            printf("%.12lf\n", dmin);
    }
}