Final answer:
The domain of the function includes 4, and 60 is in the range of the function.
Step-by-step explanation:
The function y=20x represents the number of books that will fit into boxes. The variable x represents the number of boxes, and y represents the number of books.
a. The domain of the function is the set of possible values for x. Since the function is defined as y=20x, any non-negative real number can be a valid input for x. Therefore, the domain is the set of all non-negative real numbers, including 4.
b. The range of the function is the set of possible values for y. Since y=20x, any non-negative number can be obtained as a result by choosing an appropriate value for x. Therefore, 60 is in the range of the function.