#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=int(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);
    }
    return 0;
}