The mass, M, of a child can be approximated based on the height, H, of the child. The height of the child can be projected based on the child's age, A.

Question

The mass, M, of a child can be approximated based on the height, H, of the child. The height of the child can be projected based on the child's age, A. 
a) State the chain rule for the derivative of the mass with respect to age (ie. find dM/dA) 
b) Suppose that an allometric model of the mass in kg and height in m of a 6 to 10 year old male child is given by M(H)= 16.5H^2. Further suppose that the height of 6 to 10 year old male child can be approximated by the linear model H(A) = 0.065A + 0.68 where the age is given in years. Find dM/dA.

I am having trouble with coming up with the derivative and knowing where to put specific things in specific places. Please help.