#include<iostream>

using namespace std;

int main() {
    int n;
    cin >> n;
    for(int i = 0; i < n; i++) {
        long long x, y, a, b;
        cin >> x >> y >> a >> b;
        long long l = -1, r = 1e12;
        while(r - l > 1) {
            long long m = (r + l) / 2;
            if((long double)m * m + m - 2 * (long double)(y - x) / (a + b) >= 0.0) r = m;
            else l = m;
        }
        long long curx = (long long)x + (long long) a * r * (r + 1) / 2, cury = (long long)y - (long long) b * r * (r + 1) / 2;
        while (curx >= cury && r) {
            cury += r * b;
            if (curx < cury) break;
            curx -= r * a;
            if (curx < cury) {
                curx += r * a;
                break;
            }
            r--;
        }
        cout << curx << endl;
    }
}