i. ii. iii. iv. The disk x + y a is revolved about the line x = b (b> a) to generate a solid shaped like a doughnut called a torus. Find the formula of the volume of the torus. Hint: use the disk method by slicing along the y-axis. The circle x + y = a is revolved about the line x = b (b> a) to generate a surface shaped like a doughnut called a torus. Find the formula of the surface area of the torus. Plot the torus with a = 2 and b = 5 using the built-in syntax of Mathematica. Plot the torus with a = 3 and b = 4 using the built-in syntax of Mathematica.