Answer:
Below
Explanation:
A.) Finding velocity from position requires deriving it
s' = v(t) = 21t^2 + 5
B.) Now it's plug and play
v(3) = 21(3)^2 + 5
= 21(9)+5
=194m/s
C.) Same thing, well derive the v(t)
v' = 42t
D.) One more plug and play
a = 42(3)
= 126m/s^2