Simplify.

a) [[$ \left( \dfrac{a}{b} \right)^4 \cdot \left( \dfrac{a^3}{b^2} \right)^5 $]]

b) [[$ \left( \dfrac{c}{d} \right)^3 \cdot \left( \dfrac{c^4}{d^2} \right)^6 $]]

c) [[$ \left( \dfrac{e^4}{f^2} \right)^3 \cdot \left( \dfrac{e^4}{f^2} \right)^4 $]]