#include <bits/stdc++.h>

using namespace std;

void solve() {
	long long y, s, ly, ls;
	cin >> y >> ly >> s >> ls;
	
	
	if(s <= ls) {
		cout << s * y << '\n';
		return;
	}
	
	long long res = min(abs(y - ly) * s + ls * ly, s * y);
	res = min(res, abs(y - ly) * ls + y * ls);
	if(y != ly)
	{
		long long dist = abs(ly - y);
		{
			long long opt = dist * ls  / (s - ls);
			
			for(int d = -2; d < 3; ++d) {
				long long move = opt + d;
				if(move < 1) continue;
				if(move > y) continue;
				
				res = min(res, max(move * s, (dist + move - 1) * ls) + (y - move) * ls + ls);
			}
				
		}
		{
			long long opt = (dist - 1) * ls  / (s - ls);
			
			for(int d = -2; d < 3; ++d) {
				long long move = opt + d;
				if(move < 1) continue;
				if(move > y) continue;
				
				res = min(res, max(move * s, (dist + move - 1) * ls) + (y - move) * ls + ls);
			}
				
		}
	}
	cout << res << '\n';
}

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	
	int t;
	cin >> t;
	while(t--) solve();
	
}