import sys
input = sys.stdin.readline

T=int(input())

for tests in range(T):
    N,K=list(map(int,input().split()))
    A=list(map(int,input().split()))

    ANS=1<<63

    for i in range(N):
        score=1

        for j in range(N):
            if i==j:
                score*=A[j]-K
            else:
                score*=A[j]

        ANS=min(ANS,score)

    print(ANS)