#include <bits/stdc++.h>
using namespace std;
int T, n, m, x[105], y[105], ans;
int main() {
    scanf("%d", &T);
    while (T--) {
        scanf("%d%d", &n, &m);
        ans = 1000000;
        for (int i = 1; i <= n; i++) {
            scanf("%d%d", x + i, y + i);
            ans = min(ans, ((m - 1) / x[i] + 1) * y[i]);
        }
        printf("%d\n", ans);
    }
    return 0;
}