Calculate.

a) [[$ \dfrac{2^4 \cdot 2^5}{2^6\cdot 2} = $]]

b) [[$ \dfrac{3^2 \cdot 3^3 \cdot 3^4}{3^2 \cdot 3^5} = $]]

c) [[$ \dfrac{4^4 \cdot 4^3 \cdot 4}{4^2\cdot 4^6} = $]]

d) [[$ \dfrac{10^{18}}{10^7 \cdot 10^{12}} = $]]