Final answer:
The domain of the function f(x) for 0 ≤ x ≤ 20 is [0, 20], inclusive.
Step-by-step explanation:
The domain of the function f(x) for 0 ≤ x ≤ 20 is [0, 20], inclusive. Since the graph of f(x) is a horizontal line, the function is defined for all x values between 0 and 20.