Can some one please explain how do solve this please and thank you 8-11

Which statements regarding the diagram are true? check all that apply.

Acircular city park has a sidewalk directly through the middle that is 111 - feet long. if each bag of fertilizer covers 50 square feet, then determine how many bags of fertilizers the parks and recreation department needs to use to cover the circular park. ignore all the sidewalks around and through the park.

What is the missing step in this proof ?