John can paint his home exterior in 16 hours alone. if John starts painting 2 hours before Pattie joins him, they can finish the job in 8 mroe hours. How long would it take Pattie if she painted the home exterior alone?

A) 18 hours
B) 20 hours
C)21 1/3 hours
D)20.5 hours
E) None of the above

PLEASE EXPLAIN YOUR ANSWER. It would be much appreciated.