A construction worker drops a bolt while working on a high rise building 320m above the ground. After t seconds, the bolt has fallen a distance of s metres, where s(t) = 320 - 5t^2, 0 < t < 8.

a. Find the avg. velocity during the first, third, and eighth seconds.

b. Find the avg. velocity for the interval 3 < t < 8.

c. Find the velocity at t = 2.

How do I do this problem?