#include<bits/stdc++.h>
using namespace std;
int main(){
    int T; scanf("%d",&T);
    while (T--){
        int n,m; scanf("%d%d",&n,&m);
        int ans=1e9;
        for (int i=1;i<=n;i++){
            int x, y;
            scanf("%d%d",&x,&y);
            ans=min(ans,(m+x-1)/x*y);
        }
        printf("%d\n",ans);
    }
}