6 A particle moves in a straight line such that its displacement from a fixed point after t seconds is s metres where s(t) = 1012 - 3. a Find the average velocity of the particle in the first 3 seconds. b Find the velocity and acceleration of the particle at 1 = 3s. Determine whether the particle is speeding up or slowing down at t = 3s. d Find the value of / when the particle changes direction