import sys

def fx2(day, team, cost_ls):
    if team == 1 :
        return min(cost_ls)

    min_cost_list = []  #  for result
    loop_cnt = day - team + 1
    tmp_sum = []

    k = sum(cost_ls[0:team])
    for i in xrange(len(cost_ls) - team):
        k = k - cost_ls[i] + cost_ls[i+team]
        tmp_sum.append(k)

    min_cost_list.append(min(tmp_sum)/float(team))
    team += 1
    loop_cnt -=  1

    for loop in xrange(loop_cnt,0,-1):
        tmp_sum2 = [ tmp_sum[i] + cost_ls[team+i-1] for i in xrange(loop) ]
        tmp_sum = tmp_sum2
        min_cost_list.append(min(tmp_sum)/float(team))
        team += 1

    return min(min_cost_list)


def main():
    test_count = sys.stdin.readline()
    test_count = int(test_count)

    day_team_ls = []
    cost2 =[]

    for i in xrange(test_count):
        day_team = sys.stdin.readline()
        cost = sys.stdin.readline()
        day_team_ls.append(day_team)
        cost2.append(cost)


    for i in xrange(test_count):
        day, team = day_team_ls[i].split()
        day = int(day)
        team = int(team)
        cost = [int(x) for x in cost2[i].split()]

        print fx2(day, team, cost)


if __name__ == '__main__':
    main()