#include "bits/stdc++.h"
#include "atcoder/all"
using namespace std;
using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
using mint = modint998244353;
const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
struct dat {
	int idx, a, x;
	bool operator< (const dat &right)const {
		return a * (right.x + 1) < right.a * (x + 1);
	}
};
mint calc(vector<int>&a, vector<int>&x, int &k) {
	mint ans = 1;
	rep(i, k)ans *= i + 1;
	rep(i, a.size()) {
		mint sub = 1;
		rep(j, x[i]) sub *= j + 1;
		ans *= sub.inv();
	}
	rep(i, a.size()) ans *= pow_mod(a[i], x[i], mod);
	{
		int sum = 0;
		rep(i, a.size()) sum += a[i];
		int pw = pow_mod(sum, k, mod);
		ans *= ((mint)pw).inv();
	}
	return ans;
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int t; cin >> t;
	while (t--) {
		int n, k; cin >> n >> k;
		vector<int>a(n), x(n);
		rep(i, n)cin >> a[i];
		priority_queue<dat> pq;
		rep(i, n)pq.push(dat{ i,a[i],x[i] });
		rep(i, k) {
			auto p = pq.top();
			pq.pop();
			x[p.idx]++;
			pq.push({ p.idx,a[p.idx],x[p.idx] });
		}
		cout << calc(a, x, k).val() << endl;
	}
	return 0;
}