Answer:
B. $7.50
Explanation:
We know profit or P-----P(n) where n is the quantity/number of the item) is the difference of the revenue-----R(n)-----and the cost-----C(n)
P(n) = R(n) - C(n)
Revenue is
- the product of price (p) of the item and,
- number/quantity (n) of the item:
R(n) = pn
Cost is a combination of
- fixed costs (represented by a constant (c), as the business or Indvidual making a profit must pay a certain cost, even if they don't make any of their items) and,
- variable costs (this costs changes depending on the number/quantity of the item and is the product of the marginal cost (m) and the number/quantity (n) of the item)
The cost function resembles a linear equation:
C(n) = mn + c
Since we're shown that P = 7.5n - (2.25n + 15), we know that R(n) must be R(n) = 7.5n and C(n) must be C(n) = 2.25n + 15
Thus, we know she charges $7.5 per necklace sold.