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

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

        solve(arr, k) |> println
    end
end
main()