#include <bits/stdc++.h>
using namespace std;
int main() {
    int T;
    scanf("%d", &T);
    while (T--) {
        int n, m;
        scanf("%d%d", &n, &m);
        int ans = 0x3f3f3f3f;
        for (int i = 1; i <= n; i++) {
            int x, y;
            scanf("%d%d", &x, &y);
            ans = min(ans, y * ((m + x - 1) / x));
        }
        printf("%d\n", ans);
    }
    return 0;
}