#include <bits/stdc++.h>

using namespace std;
using ll = long long;
constexpr ll mod = 998244353;
constexpr int N = 8005;

ll fact[N];

int S[N][N];

ll modPow(ll x, ll n) {
    if (!n)return 1;
    ll u = modPow(x, n / 2);
    u = u * u % mod;
    if (n % 2) u = u * x % mod;
    return u;
}

void solve(){
    ll n,m;cin >> n >> m;
    ll total = modPow(m + 1,n);
    total -= modPow(m,n);
    total -=fact[m + 1] * S[n][m+1]%mod;
    total %=mod;
    if(total < 0)total += mod;
    cout << total * modPow(modPow(m,n),mod - 2)%mod << "\n";
}

int main() {
    cin.tie(0)->sync_with_stdio(false);
    S[0][0] = 1;
    for (ll n = 1; n < N; ++n) {
        for (ll k = 1; k <= n; ++k) {
            S[n][k] = (S[n - 1][k] * k + S[n - 1][k - 1]) % mod;
        }
    }
    fact[0]=1;for(ll i = 1;i < N;++i)fact[i] = i * fact[i-1]%mod;
    int t;
    cin >> t;
    while (t--)solve();
}