#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;
}

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NgoxIDMKMwoyIDEwCjEgMQozIDEKMSAyIDMKMyAyCjEgMiA0CjQgNQoyIDIgMiAxNgo0IDUKMiAyIDIgMwo=

6
1 3
3
2 10
1 1
3 1
1 2 3
3 2
1 2 4
4 5
2 2 2 16
4 5
2 2 2 3