Final answer:
The rule that describes the piecewise-defined function is f(x) = 20 for 0 ≤ x ≤ 20. This means that for any x value between 0 and 20 (inclusive), the function will output the value 20.
Step-by-step explanation:
The rule that describes the piecewise-defined function is:
f(x) = 20 for 0 ≤ x ≤ 20
This means that for any x value between 0 and 20 (inclusive), the function will output the value 20.
For example, if we plug in x = 10, the function will still output 20.