Evaluate the surface integral. ff y d3, S is the helicoid with vector equation r(u, v) = (u cos(v), u sin(v), v), 0 S u s 1, 0 5 v 5 a: s S Consider F and C below. F(x, y) = (8 + 2xy )i+ 2x yj, C is the arc of the hyperbola y = _ from (1, 1) to |2, X 2 (a) Find a function f such that F = Vf. f ( x, y) (b) Use part (a) to evaluate - F . dr along the given curve C