If $f(x,y)=y^2-ln(xy),$ find the following.

$($a$)\frac{de{l}^{2}f}{del{x}^2}=$

$($b$)\frac{de{l}^{2}f}{\text{d}\text{e}\text{l}\text{y}\text{d}\text{e}\text{l}\text{x}}=$

$($c$)\frac{de{l}^{2}f}{\text{d}\text{e}\text{l}\text{x}\text{d}\text{e}\text{l}\text{y}}=$

$($d$)\frac{de{l}^{2}f}{del{y}^2}=$