from math import prod


def solve():
    N, K = [int(s) for s in input().split()]
    A = [int(s) for s in input().split()]

    print(
        min(prod([a - K if j == i else a for j, a in enumerate(A)]) for i in range(N))
    )


if __name__ == "__main__":
    T = int(input())

    for _ in range(T):
        solve()