#include <iostream>
#include <cmath>

using namespace std;

int T, L, R, A, B;

int main() {
    cin >> T;
    while (T--) {
        cin >> L >> R >> A >> B;
        int x = floor((R - B) / (double) A);
        int y = ceil((L - B) / (double) A);
        if (x < y) {
            cout << B << endl;
        } else {
            cout << max(A * x + B, A * y + B) << endl;
        }
    }
    return 0;
}