#include <bits/stdc++.h>
using namespace std;

#define int long long
#define debug(x) cout<<#x<<" "<<x<<endl;

const int N=1e6+5;
const double eps=1e-9;
const int INF=1e18;

signed main()
{
    //freopen("a.in","r",stdin);
    //freopen("a.out","w",stdout);
    int t;cin>>t;
    while(t--){
        int n,m;
        cin>>n>>m;
        int ans=1e9;
        for(int i=1;i<=n;i++){
            int x,y;
            scanf("%lld%lld",&x,&y);
            int ax=m/x;
            if(m%x) ax++;
            ans=min(ans,ax*y);
        }
        printf("%lld\n",ans);
    }
    return 0;
}

//Created Time  :2020/7/19 14:00:44