modelling with polynomials and rational functions

anzgurl

4 The height, x metres, of a diver above a swimming pool at time t seconds after he has bounced from the diving board can be modelled by the function x(t)= 3- 3t (3t^2/2)
a How long, in seconds, after he has bounced from the diving board does the diver
reach his maximum height?
b What is the maximum height reached by the diver, in metres?
c After exactly how many seconds does he hit the water?
d How deep is the diver half a second after he hits the water, assuming that the model
remains valid for this time?
Give your answer to the nearest centimetre.

i really need help with part d. i don't understand the question. could someone please help me?

thank you

Office_Shredder

If you know how long it takes for him to hit the water, just plug in t+1/2 to the polynomial.