I need to find the total surface area of the hollowed out hemisphere (picture attached), with an inner diameter of 1.86 cm and what looks like an outer radius (also what I am assuming as height) of 1.25 cm. Surface area of a sphere is 4∏r2, so half the sphere is 2∏r2. Since the outer hemisphere has a radius of 1.25 cm, its SA is 2∏(1.25cm)2. The inner hemisphere has a diameter of 1.86cm, therefore a radius of .93 cm. Inner hemisphere then as a SA of 2∏(.93cm)2. Adding the two SA, I get: 2∏(1.252+.932) = apprx. 15.25 cm2. However, the back of the book says the correct answer is apprx 17.44 cm2. So what am I doing wrong???