#include <bits/stdc++.h>
#define ll long long

using namespace std;

const int MOD = 1e9 + 7;

void solve(){
	int n, k;
	cin >> n >> k;
	int g = 0;

	for(int i = 0; i < n; i++){
		int x;
		cin >> x;
		g = __gcd(g, x);
	}
	if(n == 1){
		cout << k - (k <= g) << "\n";
	
		return;
	}
	
	int cur = 0;
	int cnt = 0;
	
	for(int i = 1; i < n; i++){
		if(cnt + (g - 1) >= k){
			cout << cur + (k - cnt) << "\n";
			return;
		}
		cur += g;
		cnt += (g - 1);
	}
	cout << cur + (k - cnt) << "\n";
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int t = 1;
	cin >> t;
	
	for(int i = 1; i <= t; i++){
		solve();
	}
	return 0;
}