#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9+2;
int T,n,m,x,y,res;

int main (){
   // freopen("in.txt","r",stdin);
    cin >> T;
    while(T--){
        res = INF;
        cin >> n >> m;
        for (int i=0; i<n; i++){
            cin >> x >> y;
            res = min(res, (int)ceil(1.0*m/x)*y);
        }
        cout << res << endl;
    }
    return 0;
}