This is a simple question to solve.
First, let's write our equation:
As we can see above, the total salary (S) is equal to the monthly salary (U$ 1900) plus an additional and this additional is described as the amount of U$ 90 times the number of copies (N). Once we have our equation relation S and N (that means S depends on the value of N) to graph our equation we can try to figure some values for S given different Ns. Let's draw a table to illustrate better:
We could continue our calculation for every possible N, but we just need a few points to figure out how to graph our equation. So let's use these 4 points and graph below:
The graph above represents our equation properly remembering it is not in scale.
And that is how we can solve our question.
