I need help with b and c

Exercise 2.1.4 1. Calculate the area of the given surface S. You may assume that the area is well defined. a. S is parameterised by r(u, v) = (u cosv, usin v, v), (u, v) E [0, 1] x [0, 27]. [Re- mark: The surface S is called a helicoid.] b. S is the part of the paraboloid z = a2 - x2 - y above the plane z = 0, with a > 0 a constant. c. S is a cylinder with height h > 0 and radius a > 0. d. S is a cone with height h > 0 and base with radius a > 0