Anna buys trees from a nursery that cost $5.95 each. She has a maximum of $40 to spend on her tree purchases. The total cost, with respect to the number of trees purchased, can be modeled by a function. Select the statement that correctly describes the domain of the function.
A. The domain is the set of all integers greater than or equal to 0 and less than or equal to 6.
B. The domain is the set of all integers greater than or equal to 0 and less than or equal to 7.
C. The domain is the set of all real number greater than or equal to 0 and less than or equal to 35.7
D. The domain is the set of all real numbers greater than or equal to 0 and less than or equal to 40.