1342A - Road To Zero

using namespace std;
using ll = long long;
ll x, y, a, b;
ll solve(void)
{
    ll ans = 0;
    if (x < y)
        swap(x, y);
    if (y == 0 and x == 0)
        return 0;
    if (y == 0)
        return a * x;
    ans += a * (x - y);
    x = y;
    if (b < a * 2)
        ans += b * (x);
    else
        ans += (a * 2) * (x);
    return ans;
}
int main(void)
{
    int t;
    cin >> t;
    while (t--)
    {
        cin >> x >> y;
        cin >> a >> b;
        cout << solve() << endl;
    }
    return 0;
}