Answer:
$ 15
Step-by-step explanation:
Assuming Brittany cannot price differentiate each individual so she can either charge $15 or $10 to all. We will solve for both prices for information purposes.
Total daily revenue if she charges $15 :
15 *4 = $60 as only 4 people will buy manicures
Total daily revenue if she charges $10 :
10 * 8 = $80 all 8 people will purchase
Costs if she charges $15:
5 * 4 + 25 = $45
Costs if she charges $10:
5 * 8 + 25 = $65
So, profits
For $15 = 60 - 45 = $15
For $10 = 80 - 65 = $ 15
So both amounts result in same maximum profits.
Hope that helps.