Chapter 2.5, Problem 2.46P

If the electric field in some region is given (in spherical coordinates)by the expression $E\left(r\right)=\frac{k}{r}\left[3\hat{r}+2\sin \theta \cos \theta \sin \varphi \hat{\theta }+\sin \theta \varphi \hat{\varphi }\right]$ ,for some constant k. what is the charge density? [Answer: $3k{\in }_0\left(1+\cos 2\theta \sin \varphi \right)/r^2$ ]