#include <bits/stdc++.h>
using namespace std;
const int INF=1e9;
void Solve()
{
    int n,m;
    cin>>n>>m;
    int Ans=INF;
    for (int i=1;i<=n;++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        int v=m/x+(m%x!=0);
        Ans=min(Ans,y*v);
    }
    cout<<Ans<<endl;
}
int main()
{
    int TT;
    cin>>TT;
    for (int i=1;i<=TT;++i) Solve();
    return 0;
}