Find Outer Surface Area of Cylindrical Hole Ring

[Haftred]

A cylindrical hole is put through a ball of radius a (>b) to form a ring. I am trying to find the outer surface area of the ring. I know i am supposed to parametrise the ring in some way, as we are learning about parametrizing surfaces. But I don't really know how to go about solving this problem.

 

[Haftred]

oh the radius of the cylindrical hole is 'b'

(i already know the numerical answer, i just am having problems starting the problem)