PLEASE be respectful and don't do this for the points!

At the mission museum Mrs. Perez visited over break, there is a pond like the one below that has a ring-shaped sidewalk around it. The outer edge of the sidewalk is a circle with a radius of 10 m. The inner edge of the sidewalk is a circle with a radius of 8 m.
(a) Write and simplify an expression for the exact area of the sidewalk. (4 points possible)
(b) Find the approximate area of the sidewalk. Use 3.14 to approximate π. (3 points possible)