MOD = 998244353
inv_4 = pow(4, -1, MOD)


def solve():
    N, M = [int(s) for s in input().split()]
    print(N * (N - 1) * pow(M, N, MOD) * (M - 1) * inv_4 % MOD)


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

    for _ in range(T):
        solve()