I have these 3 problems I'm struggling on.

The first:

(2y^3)(7x^2)(2y^4)

and

-m^2(4r^3)(12r^4)(5m)

and a word problem

Each side of a cube has a length given by the expression 3x^3 find the volume.

Can you guys show me how to set it up and do the problems step by step?

Thanks for your help!