The components of a mass flow vector $u$ are $u=4x^{2}y,v=xyz,w=y{z}^2$

a$)$ Compute the next mass outflow through the closed surface formed by the

planes

$x=0,x=1,y=0,y=1,z=0,z=1$

b$)$ Compute grad$*(u)$ and integrate over the volume bounded by the surface

defined in part a$).$

c$)$ Explain why the results in parts a$)$ and b$)$ should be equal or unequal.