A race car starts from rest and travels east along a

Question

Question: A race car starts from rest and travels east along a straight and level track. For the first 5.0 s of the car's motion, the eastward component of the car's velocity is given by vx(t)=(0.950m/s³)t².

Part A: What is the acceleration of the car when vx = 12.0m/s?

Please help for the above question, completely confused!! Show each steps if possible, Thanks.