#include<bits/stdc++.h>
#define LL long long
#define rint register int
using namespace std;bool f1;
int T,n,m,f[10010],a1,b1,ans;
bool f2;int main(){
    cin>>T;
    while(T--){
        scanf("%d%d",&n,&m);
        ans=1e9;
        for(int i=1;i<=n;i++){
            scanf("%d%d",&a1,&b1);
            ans=min(ans,(m+a1-1)/a1*b1);
        }
        printf("%d\n",ans);
    }
    return 0;
}