# t = int(input())
# n = int(input())
# a = list(map(int,input().split()))
# a,b,c = map(int,input().split())
#By Tahir Huzaifa
t = int(input().strip())
for _ in range(t):
    n,k = map(int,input().strip().split())
    a = list(map(int,input().split()))
    a.sort()

    a[0]-=k
    ans = 1
    for i in range(n):
        ans*=a[i]
    print(ans)