#include <cstdio>
#include <cstring>
#include <climits>
#include <algorithm>
using namespace std;

int n, m;

int main()
{
    int T;
    scanf("%d", &T);
    while (T--)
    {
        scanf("%d%d", &n, &m);
        int ans = INT_MAX;
        for (int i = 1; i <= n; ++i)
        {
            int x, y;
            scanf("%d%d", &x, &y);
            ans = min(ans, y * (m / x + !!(m % x)));
        }
        printf("%d\n", ans);
    }
    return 0;
}