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

#define FOR(i, j, k, l) for(int i = (j); i < (k); i += (l))
#define FORD(i, j, k, l) for(int i =(j); i >= (k); i -= (l))
#define REP(i, n) FOR(i, 0, n, 1)
#define REPD(i, n) FORD(i, n, 0, 1)
typedef long long ll;
const ll INFF = (ll)1e18;
const int INF = (int)1e9;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int t; cin >> t;
    while(t--){
        ll yp, lp, ys, ls;
        cin >> yp >> lp >> ys >> ls; 
        ll ans = INFF;
        ans = min(ans, yp * ys);
        ans = min(ans, abs(yp - lp) * ys + lp * ls);
        ans = min(ans, abs(lp - yp) * ls + yp * ls);
        cout << ans << "\n"; 
    }
    return 0;
}