Among the following, an incorrect statement is a) the volume of the hollow sphere =4/3π (r^3—r^3), where r is the radius of the outer sphere and r is the radius of the inner sphere. b) the volume of the hemisphere of radius(r) is 2πr^3 c) the surface area sphere = 4πr^2 d) the surface area of a spherical shell = 4π (r^2—r^2), where r = external radius and r= internal radius please can someone say which one is incorrect