Find the divergence of each of the following vector fields.

(a) $\mathrm{div} ( \, -3x\boldsymbol{i}-2y\boldsymbol{j} \, ) =$

(b) $\mathrm{div} ( \, -3y\boldsymbol{i}+2x\boldsymbol{j} \, ) =$

(c) $\mathrm{div} ( \, 2x\boldsymbol{i}+2y\boldsymbol{j} \, ) =$

(d) $\mathrm{div} ( \, \left(3x^{2}+3y^{2}\right)\boldsymbol{i}+5xy\boldsymbol{j} \, ) =$

(e) $\mathrm{div} ( \, 5x\boldsymbol{i}-5y\boldsymbol{j} \, ) =$