This tells us that the call center can accommodate 60 callers per hour with 5 workers, 120 callers per hour with 17 workers, and no callers with only 1 worker. It also tells us that 0 workers is not an acceptable input for this function.Functions are often defined using more than one formula, where each individual formula describes the function on a subset of the domain. A function defined in this way is sometimes called a piecewise-defined function. Such functions appear often in business, biology, and physics applications. In Example 1.1.4, we use a piecewise- defined function to describe sales.