On a trip, a cyclist averaged 8 miles per hour for the first 16 miles and 10 miles per hour for the remaining 16 miles. If the cyclist returned immediately via the same route and took a total of 6.8 hours for the round trip, what was the average speed (in miles per hour) for the return trip? Choose the correct answer:
A) 9
B) 10
C) 11
D) 12
E) 13

Rationale: "the time to go 32 miles was 16 / 8 + 16 / 10 = 2 + 1.6 = 3.6 hours . the average speed for the return trip was 32 miles / 3.2 hours = 10 mph . the answer is b ."
Answer: B