#include <bits/stdc++.h>
using namespace std;

#include <atcoder/modint>
using mint = atcoder::modint998244353;

void solve() {
	long long n, m; cin >> n >> m;
	mint nC2 = n; nC2 *= n-1; nC2 /= 2;
	mint ans = nC2 * (m-1) * mint(m).pow(n) / 2;
	cout << ans.val() << '\n';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int T; cin >> T;
    while (T--) solve();
}