#include "bits/stdc++.h"
using namespace std;
const int N = 105;
const int inf = 1e9+7;

int main()
{
    ios::sync_with_stdio(false);

    int t;  cin>>t;
    while(t--){
        int n,m;  cin>>n>>m;
        int ans = inf;
        for(int i=1;i<=n;i++){
            int a,b;  cin>>a>>b;
            int sum = ((m-1)/a+1)*b;
            if(sum<ans) ans = sum;
        }
        cout<<ans<<endl;
    }
}