Simplify.

a) [[$ 4a \cdot 3a^5 \cdot 6a $]] =
b) [[$ b^3 \cdot 8b \cdot 2b^4 $]] =
c) [[$ c^6d^2 \cdot 3cd \cdot 4c^3d^4 $]] =
d) [[$ 6g^2h^5 \cdot 3g^3h^2 \cdot 2gh $]] =