#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string.h>
#include<vector>
#include<cmath>
#include<string>
#include<map>
#include<queue>
using namespace std;
typedef long long ll;
const int maxn=1e5+7;

int T;
int main (){
   cin>>T;
   while(T--){
        int n,m,ans=1e9,x,y;
        scanf("%d%d",&n,&m);
        for(int i=0;i<n;i++){
            scanf("%d%d",&x,&y);
            int h= (m%x==0) ? m/x*y :(m/x+1)*y;
            ans=min(ans,h);

        }
        printf ("%d\n",ans);




   }

}