TOM traveled the entire 20 miles trip. If he did the first 10miles of at a constant rate 12 miles per hour and the remaining trip of at a constant rate 10 miles per hour, what is the his average speed, in miles per hour?	Choose the most appropriate option:
A) 12.45 mph
B) 11.25 mph
C) 10.95 mph
D) 10.91 mph
E) 10.56 mph

Rationale: avg speed = total distance / total time = ( d 1 + d 2 ) / ( t 1 + t 2 ) = ( 10 + 10 ) / ( ( 10 / 12 ) + ( 10 / 10 ) = 120 / 11 = 10.91 mph d
Answer: D