Final answer:
The domain of the function is [0, 20] and the range is a single value.
Step-by-step explanation:
The domain of the function is the set of all possible values of the input variable, which in this case is x. We are given that 0 ≤ x ≤ 20, so the domain is the interval [0, 20].
The range of the function is the set of all possible values of the output variable, which in this case is f(x). Since the graph of f(x) is a horizontal line, the output value is constant for all values of x. Therefore, the range is a single value, which is the value of f(x) for any x in the domain. In this case, the range is the value of f(x) for any x between 0 and 20, inclusive.