What is the volume of a sphere if it's greater circle has an area of 9pi cm?

Area of circle = π · r²
               9 π  = π · r²
                   9 = r²
                   3 = r

Volume of sphere = (4/3)π · r³
                             = (4/3)π · (3)³
                             = 4π · 3²
                             = 4π · 9
                             = 36π

the volume of the sphere is 36π