#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
using ul = unsigned long long;
using ll = long long;
using ld = long double;
using pll = pair<ll,ll>;
#define in(v,c) ((c).find(v) != (c).end())
#define F(i,n) for(ll i = 0; i < (ll)(n); i++)
#define Fun(i,n) for(ul i = 0; i < (n); i++)
#ifdef GPD
template<class F>void lerr(F&&f){cerr<<forward<F>(f)<<endl;}
template<class F,class...R>void lerr(F&&f,R&&...r){cerr<<forward<F>(f)<<' ';lerr(forward<R>(r)...);}
#else
#define lerr(...)
#endif

ll yp, lp, ys, ls;

int main()
{
    ll T;
    cin >> T;
    while(T--){
        cin >> yp >> lp >> ys >> ls;

        ll time_vytah = (abs(yp - lp) + yp) * ls;
        ll time_you = yp*ys;
        ll time_to_lift = abs(yp-lp)*ys + lp*ls;
        ll mina = min(time_you, time_to_lift);
        cout << min(mina, time_vytah) << endl;
    
    }

    return 0;
}