In order to win an auto race, you have to have an average speed of 100 mi/hr over the course. You travel the first half of the course at 50 mi/hr. What average speed do you need for the second half of the course?

A. 50 mi/hr

B. 150 mi/hr

C. 200 mi/hr

D. infinity (i.e., it’s impossible to go fast enough to average 100 mi/hr)