Final answer:
The question pertains to the scheduling and frequency of calls received by a unit. It involves calculating average time between calls, probabilities of calls occurring within certain time periods, and probabilities of a specific number of calls within a given time frame.
Step-by-step explanation:
The question is related to the scheduling and frequency of calls received by a unit. Based on the provided information, the average time between successive calls is calculated to be 0.25 minutes or 15 seconds. The probability that the next call occurs in less than 10 seconds is given by the cumulative distribution function. To find the probability that it takes more than three minutes for the next call to occur after a call is received, the average time between calls can be used. Ninety percent of all calls occur within a certain time frame, and the probability of the next call occurring within the next minute can be determined. The probability that fewer than 20 calls occur within an hour can also be calculated using the given information.