please guys help me this question, how to solve it.

Question

Calculate the total surface area of a hollow cylinder whose radius is 15 cm and height is 20 cm.

What formula can be applied between
(a) SA = 2pie*r*h + 2pie*r^2
(b)SA = 2pie*r*h
State the reason why you choose (a) or (b).

Answer 1

not (a) since the ends are not included
not (b) since there is an inside and an outside

and it's pi not "pie"

Answer 2

As = 2*(pi*r^2) + 2pi*r*h.
My choice is "a" , because it includes the area of the circular ends and the
area due to the ht. of the cylinder.