#include <iostream>

using namespace std;

int main()
{
    int group;
    cin >> group;
    for(int i=0; i<group; i++)
    {
        int n, m;
        cin >> n >> m;
        int ans = -1;

        int water;
        int cal;
        int need;
        int bottle;

        for(int j=0; j<n; j++)
        {
            cin >> water >> cal;
            if(m % water == 0){
                bottle = m / water;
            }
            else{
                bottle = m / water + 1;
            }
            
            if(ans == -1){
                ans = bottle * cal;
            }
            else{
                ans = min(ans, bottle * cal);
            }
        }

        cout << ans << endl;
    }
}