(6 points) A particle moves according to the law of motion s(t) = t - 6t + 4t, t 2 0, where t is measured in seconds and s in feet. a.) Find the velocity at time t. Answer: 312 - 12t + 4 b.) What is the velocity after 3 seconds? Answer: -5 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 t1 = and t2 = with t1 Note: You can earn partial credit on this