Explanation:
Let's establish our equation first:
- for every $5 decrease, there's an additional of 4 MP3 players sold.
- to get the monthly revenue, we need to multiple the cost of each player to the number of units sold
![(40mp3)/(month) * (90dollars)/(mp3) = 3600 (dollars)/(month)](https://img.qammunity.org/2022/formulas/mathematics/high-school/1od1hdpgfsgnnai8bgq1afx43lf3r5urfd.png)
The equation above is for the basis month.
But the next month, we decreased the cost of mp3 player to sold 4 more units.
![((40 + 4)mp3)/(month) * ((90 - 5)dollars)/(mp3) = 3740 (dollars)/(month)](https://img.qammunity.org/2022/formulas/mathematics/high-school/9pjx2qebnftuse6a5pzrq1ks4ryu1wq3y2.png)
And the next month, we decreased the cost again to gain 4 more additional units sold.
![((40 + 4x)mp3)/(month) * ((90 - 5x)dollars)/(mp3) = revenue per \: month](https://img.qammunity.org/2022/formulas/mathematics/high-school/92qo8gg6unxd1phhyzh1mbz9nymol5d4zx.png)
If we substitute x with 2, we get 3840.
If we substitute x with 3, we get 3900.
If we substitute x with 4, we get 3920.
If we substitute x with 5, we get 3900.
At fifth time we decreased our price, we also got lesser revenue.
Therefore, our highest revenue would be $3,900.00 per month at our 4th price decrease with a price of $70.00.