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

using ll = int64_t;
using ul = uint64_t;
using vi = vector<int>;
using vd = vector<double>;
using vc = vector<char>;
using vs = vector<string>;
using vb = vector<bool>;
using vl = vector<ll>;
using vul = vector<ul>;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using sei = set<int>;
using sec = set<char>;
using sel = set<ll>;
using vvi = vector<vi>;
using vvd = vector<vd>;
using vvc = vector<vc>;
using vvb = vector<vb>;
using vvl = vector<vl>;
using mint = modint998244353;
using vm = vector<mint>;

mint pm(mint b, ll e) {
  if (e == 0) {
    return 1;
  }
  else if (e%2 == 0) {
    mint bef = pm(b, e/2);
    return bef*bef;
  }
  else {
    return pm(b, e - 1)*b;
  }
}

int main() {
  int T;
  cin >> T;
  for (int _ = 0; _ < T; _++) {
    ll N,M;
    cin >> N >> M;
    mint n = N, m = M;
    mint p = n*(n - 1)/2;
    mint l = m*(m - 1)/2*m;
    mint unmodded = (m + 1)*m/2;
    mint modded = m*m - unmodded;
    mint result = p*(2*l - m*modded)*pm(M, N - 2);
    cout << result.val() << endl;
  }
  return 0;
}