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

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>;

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

int main() {
  ll mod = 998244353;
  int T;
  cin >> T;
  for (int _ = 0; _ < T; _++) {
    ll N,M;
    cin >> N >> M;
    if (N == 1) {
      cout << 0 << endl;
      continue;
    }
    ll n = N%mod, m = M%mod;
    ll p = (n*(n - 1)/2%mod + mod)%mod;
    ll l = ((m*(m - 1)/2%mod + mod)%mod)*m%mod;
    ll unmodded = (m + 1)*m/2%mod;
    ll modded = ((m*m%mod - unmodded)%mod + mod)%mod;
    ll result = (p*((2*l%mod - m*modded%mod)%mod + mod)%mod)*pm(m, N - 2, mod)%mod;
    result = (result + mod)%mod;
    cout << result << endl;
  }
  return 0;
}