Final answer:
The function f(x) is a horizontal line and can be represented by the equation y = 13x.
Step-by-step explanation:
The given question is about a function f(x) defined on the interval 0 ≤ x ≤ 20. The graph of f(x) is a horizontal line because the product of f multiplied by a constant equals a constant. Therefore, the value of f will remain the same for all x values between 0 and 20.
For the given options, the only function that represents a horizontal line is y = 13x. Hence, the correct statement is a. y = 13x.