Hi there! The answer is $465
The total cost can be found using the formula
![15h + 40f](https://img.qammunity.org/2019/formulas/mathematics/high-school/maxuz4yln0a4rv5y6hoaewesrka4psw35n.png)
To find the amount of money Ben Frank charges, we need to plug in the data from the question.
h = number of hours worked = 7
f = number of fixtures installed = 9
![15 * 7 + 40 * 9 = 105 + 360 = 465](https://img.qammunity.org/2019/formulas/mathematics/high-school/2tao4lk5gidehajjet8b0vk9ewx67pnmfr.png)
Therefore, Ben Frank charges $465
~ Hope this helps you!