Chapter 9, Problem 31P

Consider the following steady, three-dimensional velocity field in Cartesian coordinates: $\stackrel{\to }{V}=\left(u,v,w\right)=\left(a{x}^{2}y-b\right)\stackrel{\to }{i}+cx{y}^2\stackrel{\to }{j}+d{x}^{2}y\stackrel{\to }{k}$where $a,b,c$ , and dare constants. Under what conditions is this flow field incompressible?