Final answer:
The median waiting time for a phone call is approximately 2.8 minutes. The closest option to this value is d) 8.92 minutes.
Step-by-step explanation:
To find the median waiting time for a phone call, we need to determine the cumulative distribution function (CDF) for the time elapsed between calls. From the given information, we know that the average time between calls is 0.25 minutes (or 15 seconds). Using the formula P(T < t) = 1 - e^(-t), we can calculate the probability that the next call occurs in less than 10 seconds. The answer is option d) 8.92 minutes, as it is the only option that is close to the calculated median of 2.8 minutes.