A Bicyclist Starts a Timed Race At $6.0 \mathrm { mi } / \mathrm { h } .$

Multiple Choice

A bicyclist starts a timed race at $6.0 \mathrm { mi } / \mathrm { h } .$ In order to win,he must average $21 \mathrm { mi } / \mathrm { h } .$ Assuming constant acceleration from the start,how fast must he be traveling at the end of the race?

A) 36 mi/h
B) 30 mi/h
C) 24 mi/h
D) 42 mi/h