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

const int maxx = 1e6 + 7;
long long x, y;
int main() {
    long long T; cin >> T;
    while (T--) {
        long long n, m;
        cin >> n >> m;
        long long ans = 0x3f3f3f3f;
        for (int i = 1; i <= n; i++) {
            cin >> x >> y;
            ans = min(ans, (m / x + (m%x != 0))*y);
        }
        cout << ans << endl;
    }
}