#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <algorithm>
using namespace std;

int main()
{
    int t,n,m,ans,x,y;
    scanf("%d",&t);
    while (t--)
    {
        scanf("%d%d",&n,&m);
        ans=100000000;
        while (n--)
        {
            scanf("%d%d",&x,&y);
            ans=min(ans,(m/x+(m%x!=0))*y);
        }
        printf("%d\n",ans);
    }
    return 0;
}