A fluid has constant density ρ and velocity v = zi + (y2 + 2y)j − 2xk.
(a) Calculate the particle paths (field-lines).
(b) Calculate the mass flux through the boundary of the region x2 + y2 ≤ 4 and 0 ≤ z ≤ (4−y) by direct calculation and by using the Divergence Theorem.