#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll I=1167167167167167167;
ll Q=998244353;
#define rep(i,a) for (ll i=0;i<a;i++)
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
template<class T> void print_tate(vector<T> &v) {rep(i,v.size()) cout<<v[i]<<"\n";}
void yneos(bool a){if(a) cout<<"Yes"<<"\n"; else cout<<"No"<<"\n";}

ll jyo(ll x,ll y,ll z){
  ll H=y; //ここから
       ll a=1,b=x,c=1;
       while(H>0){
         a*=2;
         if(H%a!=0){
           H-=a/2;
           c*=b;
           c%=z;
         }
        b*=b;
         b%=z;
      } //ここまで
 return c;
}

struct date{
	int ko;
	int bo;
	 bool operator<( const date& r ) const {
		 return ko*r.bo>r.ko*bo;
	 }
	 bool operator>( const date& r ) const {
	 	 return ko*r.bo<r.ko*bo;
	 }
};

void solve(){
	int N,K;
	cin>>N>>K;
	_pq <date> pq;
	ll sum=0;
	rep(i,N){
		int a;
		cin>>a;
		sum+=a;
		date x={a,1};
		pq.push(x);
	}
	ll ans_1=1,ans_2=1;
	rep(i,K){
		auto x=pq.top();
		pq.pop();
		//cout<<x.ko<<" "<<x.bo<<endl;
		ans_1*=(x.ko*(i+1))%Q;
		ans_2*=(x.bo*sum)%Q;
		ans_1%=Q;
		ans_2%=Q;
		x.bo++;
		pq.push(x);
	}
/*cout<<ans_1<<endl;
	cout<<ans_2<<endl;*/
	cout<<(ans_1*jyo(ans_2,Q-2,Q))%Q<<"\n";
}

//おちこんだりもしたけれど、私はげんきです。
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int T;
	cin>>T;
	rep(i,T) solve();
}