Hi,It would take around CNY100 to take taxi from airport to your hotel. You could also take the shuttle bus Line 2 or the Airport Express train and get off at Dongzhimen. Here, please transfer to metro Line 2 and get off at Chongwenmen station. Exit the metro station, you will find the hotel immediately.

The shuttle bus will stop at 24:00, your fried can not take it, your friend can take the Shuttle bus line 2 to Xidan and then take taxi to your hotel. That would make the trip easier.