#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define Pr pair<ll,ll>
#define Tp tuple<ll,ll,ll>
using Graph = vector<vector<int>>;

ll mod = 998244353;


//mod逆元
long long modinv(long long a, long long m) {
    long long b = m, u = 1, v = 0;
    while (b) {
        long long t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= m;
    if (u < 0) u += m;
    return u;
}

int main() {
    ll T; cin >> T;
    rep(i,T){
    ll N,K; cin >> N >> K;
    ll sum = 0;
    multiset<tuple<double,ll,ll>> num;
    rep(i,N){
        ll a; cin >> a;
        num.insert(make_tuple((double)a,a,1LL));
        sum += a;
    }
    sum %= mod;
    ll ans = 1;
    rep(i,K){
        ans *= (ll)(i+1); ans %= mod;
        ans *= modinv(sum,mod); ans %= mod;
    }
    rep(i,K){
        auto itr = num.end(); itr--;
        auto[s,a,j] = *itr;
        num.erase(itr);
        ans *= a; ans %= mod;
        ans *= modinv(j,mod); ans %= mod;
        num.insert(make_tuple(s*(double)(j)/(double)(j+1),a,j+1));
    }
    cout << ans << endl;
    }
}