#include<bits/stdc++.h>
using namespace std;
int main(){
    int t;cin>>t;
    while(t--){
        int n,m;cin>>n>>m;
        int ans=2e9;
        for(int i=1;i<=n;i++){
            int x,y;cin>>x>>y;
            ans=min(ans,((m-1)/x+1)*y);
        }
        cout<<ans<<endl;
    }
}