Final answer:
The maximum number of times the phone should ring before it is answered depends on the average number of calls received during a given time period.
Step-by-step explanation:
In order to determine the maximum number of times a phone should ring before it is answered, we need to consider the average number of calls received during a given time period.
Without that information, we cannot provide an exact answer. However, if we assume that the average is 20 calls during the peak time, then the maximum number of times the phone should ring before it is answered would be 21, as any additional rings would exceed the average.