Let
x -----> the number of books
so
Part a
Write a linear cost function C(x) for this situation.
C(x)=3.50x+600
Part b
Write a linear revenue function R(x) for this situation.
R(x)=11.00x
Part c
Write a profit function P (x) for this situation.
Remember that the profit is equal to the Revenue minus the cost
so
P(x)=R(x)-C(x)
substitute
P(x)=11.00x-(3.50x+600)
P(x)=7.50x-600
Part d
How much loss (or profit) comes from the sale of 900 books?
For x=900
substitute in the P(x) function
P(x)=7.50(900)-600
P(x)=6,150
the profit is $6,150