#include <cstdio>
#include <algorithm>
#include <iostream>
#include <ctime>
#include <cmath>
using namespace std;
int n,m,T;
int ans;
int main()
{
    scanf("%d",&T);
    for(int ii=1;ii<=T;++ii){
        scanf("%d%d",&n,&m);
        for(int i=1;i<=n;++i){
            int x,y;
            scanf("%d%d",&x,&y);
            int aug = ((m-1)/x + 1) * y;
            if(i == 1)ans = aug;
            else ans = min(ans,aug);
        }
        printf("%d\n",ans);
    }
    return 0;
 }