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

int main() {
    int t;
    cin >> t;
    while (t--) {
        int n, m;
        cin >> n >> m;
        vector<int> x(n), y(n);
        for (int i = 0; i < n; i++) {
            cin >> x[i] >> y[i];
        }
        int res = 1e9;
        for (int i = 0; i < n; i++) {
            int t = m/x[i];
            int b = t*y[i];
            if (m%x[i]) {
                b += y[i];
            }
            res = min(res, b);
        }
        cout << res << endl;
    }
}