#include<iostream>
#include<algorithm>
using namespace std;
int main(){
    int T;  cin>>T;
    while(T--){
        int n, m, ans = (int)1e9;
        cin>>n>>m;
        for(int i = 1; i <= n; i++){
            int x, y; cin>>x>>y;
            if(m%x==0)ans = min(ans, m/x*y);
            else ans = min(ans,(m/x+1)*y);
        }
        cout<<ans<<"\n";
    }
    return 0;
}