This is the expression:

C(x)=x(3x-(500+6x))

My questions are:

I am totally confused and to top it off the Chain Rule really confuses me. I can figure it out if I see an example worked out but I haven't been able to find examples that look exactly like this which makes me think I am trying to use the wrong rule.

- Am I am supposed to use the chain rule because there is a function within a function ? If so, what happens to the x outside ? Or better question: which terms/functions would be considered outside functions and which is considered an inside function ?
- Or am I supposed to use the product rule because the x is outside of the rest of the function ? (Not feeling confident about this option)

PLEASE HELP !!!!