I keep getting the answer wrong please help

The size of an unborn fetus of a certain species depends on its age. Data for Head circumference (H) as a function of age (t) in weeks were fitted using the formula H = - 30.43 + 1.867t - 0.4928t log t. dH (a) Calculate the rate of fetal growth - dt dH (b) Is dt larger early in development (say at t = 8 weeks) or late (say at t = 36 weeks)? 1 dH (c) Repeat part (b) but for fractional rate of growth H dt