/*********************************************************************
    Problem:1001
    Author:hydd
    Date:
*********************************************************************/
#include<cstdio>
#include<algorithm>
#define File(x) freopen(x".in","r",stdin);freopen(x".out","w",stdout);
using namespace std;
int T,n,m,ans,u,v;
int main(){
    scanf("%d",&T);
    while (T--){
        scanf("%d%d",&n,&m); ans=0x3f3f3f3f;
        for (int i=1;i<=n;i++){
            scanf("%d%d",&u,&v);
            ans=min(ans,(m+u-1)/u*v);
        }
        printf("%d\n",ans);
    }
    return 0;
}