Find the divergence of each of the following vector fields at all points where they are defined.

(a) $\displaystyle \mathrm{div} \left( \, \frac{x}{\left(x^{2}+y^{2}+z^{2}\right)^{1.5}}\boldsymbol{i}+\frac{y}{\left(x^{2}+y^{2}+z^{2}\right)^{1.5}}\boldsymbol{j}+\frac{z}{\left(x^{2}+y^{2}+z^{2}\right)^{1.5}}\boldsymbol{k} \, \right) =$

(b) $\displaystyle \mathrm{div} \left( \, \left(2x^{2}-\sin\!\left(xz\right)\right)\boldsymbol{i}+4\boldsymbol{j}-\sin\!\left(xz\right)\boldsymbol{k} \, \right) =$

(c) $\displaystyle \mathrm{div} \left( \, 2e^{xy}\boldsymbol{i}+5\cos\!\left(xy\right)\boldsymbol{j}+5e^{\ln\!\left(x^{2}+y^{2}+4\right)}\boldsymbol{k} \, \right) =$