Ken's average speed for a trip is 14 miles per hour. During the first part of the trip, he traveled at 15 miles per hour for 2 hours, and then traveled at a different speed for 1 hour the rest of the way. What was her speed for the second part
of the trip?
A. 7.5 mph
B. 12.0 mph
C. 15.0 mph
D. 22.5 mph