#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
using namespace std;

int T,n,m,x,y,ans,cnt;

int main()
{
    cin >> T;
    for (int i = 1;i<=T;++i)
    {
        cin >> n >> m;
        ans = -1;
        for (int j = 1;j<=n;++j)
        {
            cin >> x >> y;
            cnt = (m % x == 0 ? m / x : m / x + 1) * y;
            if (ans == -1 || cnt < ans) ans = cnt;
        }
        cout << ans << endl;
    }
    return 0;    
}