#include <bits/stdc++.h>

using namespace std;

int main()
{
    int kase;
    scanf("%d", &kase);
    while (kase--)
    {
        int n, m, ans = INT_MAX;
        scanf("%d%d", &n, &m);
        while (n--)
        {
            int x, y;
            scanf("%d%d", &x, &y);
            int c = (m + x - 1) / x;
            ans = min(ans, c * y);
        }
        printf("%d\n", ans);
    }
}