Need help with three separate parts:

We'll be analyzing the surface area of a round cylinder - in other words the amount of material needed to "make a can".

A cylinder (round can) has a circular base and a circular top with vertical sides in between. Let (r) be the radius of the top of the can and let (h) be the height. The surface area of the cylinder, A, is A=2(r)^2+2(r)(h).

Part A: Assume that the height of your cylinder is 8 inches. Consider A as a function of r, so we can write that as A(r)=2(r)^2+16(r). What is the domain of A(r)? In other words, for which values of r is A(r) defined?

Part B: Continue to assume that the height of your cylinder is 8 inches. Write the radius r as a function of A. This is the inverse function to A(r), i.e to turn A as a function of r into r as a function of A.

Part C: If the surface area is 175 square inches, then what is the radius r? In other words, evaluate r(175)?

Please provide step by step instructions! Really stumped as to how to complete this and looking to understand. Thanks!