#include<bits/stdc++.h>
using namespace std;
const int N=1e4+10;

int n,m,T;

int main()
{
    cin>>T;
    while(T--)
    {
        int ans=INT_MAX;
        cin>>n>>m;
        for(int i=1;i<=n;i++) 
        {
            int x,y;
            cin>>x>>y;
            int k=(m+x-1)/x;
            int t=k*y;
            ans=min(ans,t);
        }
            cout<<ans<<endl;
    }
    
            return 0;
}