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

int T, n, m;

int main() {
    cin >> T;
    while (T--) {
        cin >> n >> m;
        int ans = 0x3f3f3f3f;
        for (int i = 1; i <= n; i++) {
            int x, y;
            cin >> x >> y;
            int z = (m + x - 1) / x;
            ans = min(ans, z * y);
        }
        printf("%d\n", ans);
    }
}