A wok frying pan is shaped like a spherical bowl with handles. A bit of experimentation at home persuades a cook that a wok holds about 3 L if it is 9 cm deep and the sphere has a radius of 20 cm. To be sure, picture the wok as a solid of revolution, as shown in the figure, and calculate its volume with an integral. What is the real volume of the wok? (1L=1000cm^3)