A Car Accelerates Uniformly from Rest to a Speed of 20

Multiple Choice

A car accelerates uniformly from rest to a speed of 20 m/s at the end of 1 min; it then accelerates uniformly to a speed of 40 m/s at the end of the next minute.During this 2-min period,the average speed of the car is

A) 7.5 m/s
B) 30 m/s
C) 15 m/s
D) 20 m/s
E) 40 m/s