Can anyone help? I am stuck on one piece of an answer I was given in a CH document: Given the following facts, how do I calculate Marginal Revenue?

Type of firm: Monopoly Firm

The firm maximizes profits.

Average revenue (demand) curve: P = 360 0.04Q

Cost function: C = 60Q + 5000.

Marginal cost (MC) of production: $60.

Q=output

P=price in dollars

C=cost

I was given by a Course Hero solution:

MR=8/8Q*TR

=8/8Q*(360Q-0.04Q²)

=360-0.08Q

In the above answers given, I don't understand where 8/8Q and 0.08Q came from. I really want to master this material, but I felt lost here. Thanks for any help!