Subject: mathqa
Question: tom traveled the entire 60 miles trip . if he did the first 15 miles of at a constant rate 24 miles per hour and the remaining trip of at a constant rate 45 miles per hour , what is the his average speed , in miles per hour ?
Option: 
A: 34.52 mph
B: 36.92 mph
C: 36.29 mph
D: 35.62 mph
Answer: B