simplify each of the following.
[tex] {a) \: } \frac{ {8}^{5}y}{12x {}^{3} {y}^{4} } [/tex]

[tex] {}^{b)} \frac{ {9x}^{4} {(x - y)}^{3}}{27 {x}^{2} {y}^{3}(x - y) } [/tex]