#include<bits/stdc++.h>
using namespace std;
const int N=1000005;
int t,n,m,i,dp[10105],j;
struct str{
    int x,y;
}a[N];
int main(){
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d %d",&n,&m);
        int ans=1<<30;
        for(i=1;i<=n;++i)
        {
            scanf("%d %d",&a[i].x,&a[i].y);
            ans=min(ans,(m+a[i].x-1)/a[i].x*a[i].y);
        }
        cout<<ans<<endl;
    }
}