#include<bits/stdc++.h>
using namespace std;
int T,n,m,ans,a,b;
main()
{
    cin>>T;
    while(T--)
    {
        cin>>n>>m;
        ans=1e9;
        while(n--)cin>>a>>b,ans=min(ans,(m+a-1)/a*b);
        cout<<ans<<endl;
    }
}