For each of the following vector fields f, decide whether it is conservative or not by computing the appropriate first order partial derivatives. type in a potential function f (that is, nabla f = f) with f(0,0) = 0. if it is not conservative, type n. a f (x, y) = (6x - 2y)i + (-2x + 8y)j f (x, y) = b. f (x, y) = 3yi + 4xj f (x, y) = n c. f (x, y) -= (3siny)i + (-4y + 3x cosy)j f(x, y) =