A particle moves from point O along a straight line such that its acceleration at any time, t seconds is \(a = (4 - 2t) ms^{-2}\). At t = 0, its distance from O is 18 metres while its velocity is \(5 ms^{-1}\).

(a) At what time will the velocity be greatest?

(b) Calculate the : (i) time ; (ii) distance of the particle from O when the particle is momentarily at rest.