Please help with Calculus question

The function s(t) describes the motion of a particle along a line. s(t) = t3 14t2 + 32: 255 (a) Find the velocity function v(t) of the particle at any time t 2 0. (b) Identify the time interval in which the particle is moving in a positive direction. 0 (0, on) O (0, 8) O (0, 4/3) 0 (0, 4/3), (8, 00) O (4/3, 8) 0 None (c) Identify the time interval in which the particle is moving in a negative direction. 0 (0, can) 0 (0, B) O (0, 4/3) 0 (0, 4/3), (8, 00) O (4/3, 3) 0 None (d) Identify the time(s) at which the particle changes direction. (Enter your answers as a comma-separated list.)