#include<bits/stdc++.h>
using namespace std;
int main()
{
    int test;
    cin>>test;
    while(test--){
        int n,m;
        cin>>n>>m;
        int res=INT_MAX;
        while(n--){
            int x,y;
            cin>>x>>y;
            int temp=m%x;
            if(temp==0){
                int sum=m/x;
                res=min(res,sum*y);
            }
            else{
                int sum=m/x+1;
                res=min(res,sum*y);
            }
        }
        cout<<res<<endl;
    }
    return 0;
}