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

//* ATCODER
#include<atcoder/all>
using namespace atcoder;
typedef modint998244353 mint;
//*/

/* BOOST MULTIPRECISION
#include<boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
//*/

typedef long long ll;

#define rep(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
#define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--)

template <typename T> bool chmin(T &a, const T &b) {
	if (a <= b) return false;
	a = b;
	return true;
}

template <typename T> bool chmax(T &a, const T &b) {
	if (a >= b) return false;
	a = b;
	return true;
}

template <typename T> T max(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmax(ret, a[i]);
	return ret;
}

template <typename T> T min(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmin(ret, a[i]);
	return ret;
}

template <typename T> T sum(vector<T> &a){
	T ret = 0;
	for (int i=0; i<(int)a.size(); i++) ret += a[i];
	return ret;
}

void solve(){
	int n, m;
	cin >> m >> n;
	vector dp(n+1, vector<mint>(3));
	mint inv2 = mint(2).inv();
	dp[0][0] = 1;
	rep(i,0,n){
		dp[i+1][0] += dp[i][0];
		dp[i+1][1] += dp[i][0] * mint(m);
		if (m > 3){
			dp[i+1][2] += dp[i][0] * (mint(m) * mint(m-1) * inv2 - mint(m));
		}
		dp[i+1][0] += dp[i][1];
		dp[i+1][1] += dp[i][1] * mint(m-1);
		if (m > 3){
			dp[i+1][2] += dp[i][1] * (mint(m-1) * mint(m-2) * inv2 - mint(m-2));
		}
		dp[i+1][0] += dp[i][2];
		dp[i+1][1] += dp[i][2] * mint(m-2);
		if (m > 3){
			dp[i+1][2] += dp[i][2] * (mint(m) * mint(m) * inv2 - mint(7) * mint(m) * inv2 + 7);
		}
	}

	cout << (dp[n][0] + dp[n][1] + dp[n][2]).val() << '\n';
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	
	int t; cin >> t;
	while(t--) solve();
}