#include<bits/stdc++.h>
using namespace std;
int main()
{
    int T,n,m,x,y,ans;
    cin>>T;
    while (T--)
    {
        cin>>n>>m;
        ans=1e9+7;
        while (n--)
        {
            cin>>x>>y;
            ans=min(ans,((m-1)/x+1)*y);
        }
        cout<<ans<<'\n';
    }
}