#include <bits/stdc++.h>
using namespace std;

#define st first
#define nd second
#define pb push_back
using ll = long long;
using db = double;
using ldb = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

void solve(){
    ll yp, lp, ys, ls;
    cin >> yp >> lp >> ys >> ls;
    if(ys <= ls || lp >= yp){
        cout << min(yp * ys, lp * ls) << "\n";
        return;
    }
    ll dif = abs(yp - lp);
    ll predkosc = ys + ls;
    ll meet = yp - ((ls * dif) / (predkosc));
    ll best = yp * ys;
    for(ll i=meet-5;i<=meet+5;i++){
        if(i <= 0) continue;
        ll jaDif = abs(yp - i);
        ll wDif = abs(lp - i);
        ll czas = 0;
        czas += max(jaDif * ys, wDif * ls);
        czas += ls * i;
        best = min(best, czas);
    }
    cout << best << "\n";
}

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