Final answer:
A function is continuous at a given value if the limit of the function as it approaches that value exists and is equal to the value of the function at that point.
Step-by-step explanation:
A function is continuous at a given value if the limit of the function as it approaches that value exists and is equal to the value of the function at that point. To determine if a function is continuous at a given value, we need to evaluate the limit of the function as it approaches that value. If the limit exists and is equal to the value of the function at that point, then the function is continuous at that value.
In this case, the function f(x) is a horizontal line between x = 0 and x = 20. Since the function is constant throughout this interval, the limit of the function as it approaches any value within this interval will be equal to the value of the function at that point. Therefore, the function is continuous at all values between 0 and 20, inclusive.