#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define bitrep(i, n) for (ll i = 0; i < (1 << n); ++i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define yesNo(b) ((b) ? "Yes" : "No")
using ll = long long;
using ull = unsigned long long;
string alphabet = "abcdefghijklmnopqrstuvwxyz";
string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const double pi = 3.141592653589793;
int smallMOD = 998244353;
int bigMOD = 1000000007;

int axB(int x, int a, int b)
{
    return a * x + b;
}

int main()
{
    int q;
    cin >> q;
    rep(i, q)
    {
        int x, y, a, b;
        cin >> x >> y >> a >> b;
        cout << max(axB(y, a, b), axB(x, a, b)) << endl;
    }
    return 0;
}