A Automotive Test Driver Travels Due North in a Prototype

Multiple Choice

A automotive test driver travels due north in a prototype hybrid vehicle at 30 mi/h for 2 hours. She then reverses her direction and travels due south at 60 mi/h for 1 hour.
-What is the average speed of the vehicle?

A) zero mi/h
B) 30 mi/h
C) 40 mi/h
D) 50 mi/h
E) 60 mi/h