A particle moves according to the law of motion , , where is measured in seconds and in feet.

a.) Find the velocity at time .
Answer:

b.) What is the velocity after seconds?
Answer:

c.) When is the particle at rest? Enter your answer as a comma separated list. Enter None if the particle is never at rest.
At and with .

d.) When is the particle moving in the positive direction?
When and

You can earn partial credit on this problem.