Find the volume charge density that is associated with each of the following fields: $($a$)$ vec$(D)=x{y}^2$hat$(a{)}_x+y{x}^2$hat$(a{)}_y+$zhat$(a{)}_z\frac{C}{m^2}$; $($b$)$ vec$(D)=z^{2}si{n}^{2}hat(a{)}_{}+z^{2}sincoshat(a{)}_{}+{}^{2}zsi{n}^{2}hat(a{)}_z\frac{C}{m^2}$; $($c$)$ Ans:

$[$:$x^2+y^2+1\frac{C}{m^3}$;$z^2+{}^{2}zsin\frac{C}{m^3}$;$\frac{2}{r}\frac{C}{m^3}$