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from itertools import combinations

def max_probability(n, required_points, probabilities):
    best_prob = 0.0
    
    for r in range(required_points, n + 1):
        for subset in combinations(range(n), r):
            prob = 1.0
            for i in range(n):
                if i in subset:
                    prob *= probabilities[i]
                else:
                    prob *= (1 - probabilities[i])
            best_prob = max(best_prob, prob)
    
    return best_prob


t = int(input())
for _ in range(t):
    n, required_points = map(int, input().split())
    probabilities = [float(input()) for _ in range(n)]
    
    result = max_probability(n, required_points, probabilities)
    print(f"{result:.6f}")