I can't solve this problem

[winter kernel]

!status

[deft prairie]

What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above

[sharp path]

Both selling price r x and n?
There's a mistake here

[somber sage]

selling volume is x and selling price is n?