Consider the vector field F(x, y, z) = xi + yj + zk. a) Find a function f such that F = Vf and f(0, 0, 0) = 0. f(x, y, z) b) Use part a) to compute the work done by F on a particle moving along the curve C given by r(t) = (1 + 2 sint)i + (1 + sin?t)j + (1 + sint)k, 0