Question

A bookstore costs $90 a day to keep open, and spends $12 for each book it sells. the store charges $18 for each book it sells. If n represents the number of books sold, which equation represents the revenue function for this bookstore?

Answer 1

Total Cost in a day is
`TC= 90 + 12n`. Profit function is
`P=18n`. And the revenue function is
`R = P-TC = 18n-12n-90 = 6n-90`. In a day, bookstore must sell at least 15 books, because of 6n-90=0, in order to make profit.

Answer 2

`R=6n-90`

Explanation:

Let

R------> the revenue function

n------> the number of books sold per day

we know that

In this problem

`18n` -----> represent the profit

`(12n+90)` -----> represent the cost

so

The revenue is equal to the profit minus the cost

`R=18n-(12n+90)`

`R=n(18-12)-90` ------> equation that represent the revenue function

Simplify

`R=6n-90`