#include<bits/stdc++.h>
using namespace std;
int test,x,y,ans,n,m;
int main()
{
    scanf("%d",&test);
    while(test--)
    {
        scanf("%d%d",&n,&m);ans=1e9;
        for (int i=1;i<=n;i++)
        {
            scanf("%d%d",&x,&y);
            ans=min(ans,(m+x-1)/x*y);
        }
        printf("%d\n",ans);
    }
    return 0;
}