2. At a zoo, the lion exhibit has a ring-shaped sidewalk around it. The outer edge of the sidewalk is a circle with a radius of 13 m. The inner edge of the sidewalk is a circle with a radius of 11 m.

(a) Write and simplify an expression for the exact area of the sidewalk.
(b) Find the approximate area of the sidewalk. Use 3.14 to approximate π.