Earnings $=12+{5\mathrm{.}5}^{**}$ workstation $-{0\mathrm{.}5}^{**}$ shampoo price

Where earnings is the total revenue in dollars, workstation is the number of workstations at a hair salon, and shampoo price is the price of the shampoo used at the salon.

What does the model predict that the earnings will be at a salon with three workstations when the shampoo costs $$10?$

$23\mathrm{.}5$

$10\mathrm{.}5$

$34\mathrm{.}5$

$28\mathrm{.}5$