#include <bits/stdc++.h>
using namespace std;

int main() {
    int T; cin >> T;
    while (T--) {
        int n, m, ans = 1E9;
        cin >> n >> m;
        while (n--) {
            int x, y;
            cin >> x >> y;
            int cnt = (m + x - 1) / x;
            ans = min(ans, cnt * y);
        }
        cout << ans << endl;
    }
    return 0;
}