Final answer:
The domain of the given function is the closed interval from 0 to 20, including the endpoints, since the function f(x) is defined and restricted to that interval.
Step-by-step explanation:
The domain of a function is the set of all possible input values (usually x values) for which the function is defined. Considering the information provided, where the function f(x) is restricted to the interval 0 ≤ x ≤ 20, the domain is all real numbers from 0 to 20, inclusive. Thus, any values of x outside this interval, such as x < 0 or x > 20, are not part of the domain. This effectively means that for the given function, the domain is the closed interval from 0 to 20.