#### Answer

a. When the ticket price is 65 dollars, the weekly profit to the airline on flights from Boston to Washington is 15,000 dollars.
b. When the ticket price is 65 dollars, the weekly profit to the airline on flights from Boston to Washington is increasing by 1.5 thousand dollars per dollar (of ticket price).
c. When the ticket price is 90 dollars, the weekly profit to the airline on flights from Boston to Washington is decreasing by 2 thousand dollars per dollar (of ticket price).

#### Work Step by Step

a. We see the ticket price is set at 65 dollars by looking at $f(65)$ then we see that the weekly profit is 15,000 because it says that $f(65) = 15$ and the units of measure are thousand dollars.
b. We see that the ticket price is set at 65 dollars by looking at $f'(65)$, then we see it is prime so it means that we are looking at the change (in sales) per dollar. We get 1.5 thousand from looking at $f'(65)= 1.5$ and know that the units are thousand dollars.
c. We see that the ticket price is set at 90 dollars by looking at $f'(90)$, then we see it is prime so it means that we are looking at the change (in sales) per dollar. We get 2 thousand from looking at $f'(90)= 2$ and know that the units are thousand dollars.