function solve(arr, k)
    min = minimum(arr)
    minIdx = findfirst(isequal(min), arr)
    iter = (i == minIdx ? v - k : v for (i, v) ∈ enumerate(arr))
    return prod(iter)
end

function main()
    t = parse(Int, readline())
    
    for _ ∈ 1:t
        _, k = parse.(Int, split(readline()))
        arr = parse.(Int, split(readline()))

        result = solve(arr, k)

        println(result)
    end
end
main()