#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

struct combi{
	deque<mint> kaijou;
	deque<mint> kaijou_;
	
	combi(int n){
		kaijou.push_back(1);
		for(int i=1;i<=n;i++){
			kaijou.push_back(kaijou[i-1]*i);
		}
		
		mint b=kaijou[n].inv();
		
		kaijou_.push_front(b);
		for(int i=1;i<=n;i++){
			int k=n+1-i;
			kaijou_.push_front(kaijou_[0]*k);
		}
	}
	
	mint combination(int n,int r){
		if(r>n)return 0;
		mint a = kaijou[n]*kaijou_[r];
		a *= kaijou_[n-r];
		return a;
	}
	
	mint junretsu(int a,int b){
		mint x = kaijou_[a]*kaijou_[b];
		x *= kaijou[a+b];
		return x;
	}
	
	mint catalan(int n){
		return combination(2*n,n)/(n+1);
	}
	
};

combi C(1000000);

void solve(){
	int N,K;
	cin>>N>>K;
	
	vector<int> A(N);
	int S = 0;
	rep(i,N){
		cin>>A[i];
		S += A[i];
	}
	
	vector<int> v(N);
	priority_queue<pair<int,int>> Q;
	int sum = 0;
	rep(i,N){
		int t = A[i] * K;
		v[i] = t / S;
		Q.emplace(t%S,i);
		sum += v[i];
	}
	
	while(sum != K){
		sum ++;
		v[Q.top().second]++;
		Q.pop();
	}
	
	mint ans = 1;
	
	int n = K;
	
	rep(i,N){
		//cout<<v[i]<<',';
		mint p = A[i];
		p /= S;
		ans *= p.pow(v[i]);
		ans *= C.combination(n,v[i]);
		n -= v[i];
	}
	
	
	cout<<ans.val()<<endl;
	
}

int main(){
	
	int _T;
	cin>>_T;
	
	rep(_,_T){
		solve();
	}
	
	return 0;
}