#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;
using ll = long long;

#include<atcoder/modint>
using mint = atcoder::modint998244353;
// using mint = long double;
#include<math.h>
#include<queue>

void solve(){
    ll n,k;
    cin>>n>>k;
    vector<ll> a(n);
    for(int i = 0;i<n;i++) cin>>a[i];
    ll sum = 0;
    for(int i = 0;i<n;i++) sum += a[i];
    vector<ll> use(n),res(n);
    for(int i = 0;i<n;i++) {
        use[i] = (a[i]*k) / sum;
        res[i] = (a[i]*k) % sum;
    }
    vector<int> idx(n);
    for(int i = 0;i<n;i++) idx[i] = i;
    sort(idx.begin(),idx.end(),[&](int i,int j){
        if(res[i]!=res[j]) return res[i] > res[j];
        return a[i] > a[j];
    });
    ll now = 0;
    for(int i = 0;i<n;i++) now += use[i];
    now = k - now;
    for(int i = 0;i<now;i++){
        int ni = idx[i];
        use[ni]++;
    }

    for(int i = 0;i<n;i++) use[i] = 0;
    using dat = pair<long double,int>;
    priority_queue<dat> que;
    vector<long double> f(k+4,0);
    for(int i = 1;i<=k+3;i++) f[i] = f[i-1] + log(i);
    auto add = [&](int i) {
        long double nxt = (use[i]+1) * log(a[i]) - (use[i]+1) * log(sum) - f[use[i]+1];
        long double now = use[i] * log(a[i]) - use[i] * log(sum) - f[use[i]];
        que.push(make_pair(nxt - now,i));
    };
    for(int i = 0;i<n;i++) add(i);
    for(int i = 0;i<k;i++){
        auto now = que.top();
        que.pop();
        int ni = now.second;
        //cout<<now.first<<" "<<ni<<endl;
        use[ni]++;
        add(ni);
    }

    mint ans = 1;
    ll all = k;
    vector<mint> fac(k+1,0);
    fac[0] = 1;
    for(int i = 1;i<=k;i++) fac[i] = fac[i-1] * i;
    ans = fac[k];
    for(int i = 0;i<n;i++){
        mint tmp = fac[use[i]].inv();
        mint p = mint(a[i]) * (mint(sum).inv());
        p = p.pow(use[i]);

        // mint tmp = 1. / fac[use[i]];
        // mint p = (long double) a[i] / sum;
        // p = pow(p,use[i]);
        ans *= tmp * p;
    }
    cout<<ans.val()<<endl;
    return;
    for(int i = 0;i<n;i++) cout<<use[i]<<" ";
    cout<<endl;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

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