Peter is making new cushion covers for a chair. There are three sizes of cushions on the chair. What is the surface area of the seat back cushion?
21 in
Net for Seat Back
3 in
3 in
10 in
21 in
21 in
3 in
seat back
15 in
10 in arm rest
15 in
15 in
3 in
seat bottom
3 in
21 in
18 in
21 in