domain and range for the function, algebra homework help

Do the following for the function given below.

(current price of gasoline, number of tourists in a national park)

a.	Describe an appropriate domain and range for the function.
b.	Make a rough sketch of a graph of the function.
c.	Briefly discuss the validity of the graph as a model of the true function.

a. Choose the appropriate domain for the function below.

A.The domain is the numbers of tourists visiting the park or 0 people to 1 million people.

B.The domain is the numbers of tourists visiting the park or 2500 people to 15,000 people.

C.The domain is all realistic gasoline prices or $ 0.25 per gallon to $ 1.50 per gallon.

D.The domain is all realistic gasoline prices or $ 2 per gallon to $ 4 per gallon.