Use the Following to Answer Questions

Multiple Choice

Use the following to answer questions :
A driver going down a straight highway is traveling at 70 ft/sec on cruise control when he begins accelerating at a rate of 4.2 ft/sec². The final velocity of the car is given by the function , where V(t) is the velocity at time t.
-If the car is traveling at 100 ft/sec, for how long did it accelerate? (Round to the nearest tenth of a second.)

A) 6.9 seconds
B) 7.1 seconds
C) 7.3 seconds
D) 7.5 seconds