how long does it take shuttle bus 7 from beijing west train station to T3 capital airport at 9.30am?

Im arriving at the train station at 9.18am and need to get No.7 shuttle bus to Terminal 3 to catch a 12.50 flight to Harbin.

How much time does it take shuttle bus 7 to travel the train station to the airport at 9.30am ?

Thank you

Cheryl