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

void solve(){
	using mint=atcoder::modint998244353;
	using ll=long long;
	ll n,m;
	cin>>n>>m;
	if (n==1){
		cout<<0<<endl;
		return;
	}
	mint a=mint(m)*(m-1)*m/2;
	mint b=mint(n)*(n-1)/2*mint(m).pow(n-2);
	mint ans=a*b;
	cout<<ans.val()<<endl;
}

int main(){
	int t;
	cin>>t;
	while (t--) solve();
}