The Position of an Object as a Function of Time

Short Answer

The position of an object as a function of time is given by x(t) = at³ - bt² + ct - d, where
a = 3.6 m/s³, b = 4.0 m/s², c = 60 m/s and d = 7.0 m.
(a) Find the instantaneous acceleration at t =2.4 s.
(b) Find the average acceleration over the first 2.4 seconds.