#include<bits/stdc++.h>
using namespace std;
int dp[10200];
int main(){
    int T,n,m,x,y;
    cin>>T;
    while(T--){
        scanf("%d%d",&n,&m);
        memset(dp,63,sizeof(dp));
        int ans=1e9;
        for(int i = 1 ; i<=n;i++){
            scanf("%d%d",&x,&y);
            int t=m/x;
            if(m%x)t++;
            ans=min(ans,t*y);
        }
        cout<<ans<<endl;
    }
    return 0;
}