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

using namespace std;
using ll = long long;

#include<atcoder/modint>
using mint = atcoder::modint998244353;

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]++;
    }

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