7 Customers arrive at a particular shop at random times. It has been found that the mean number of customers who arrive during a 5 -minute interval is 2.1 .
- Find the probability that exactly 4 customers arrive during a 10 -minute interval.
- Find the probability that at least 4 customers arrive during a 20 -minute interval.
- Use a suitable approximating distribution to find the probability that fewer than 40 customers arrive during a 2-hour interval.
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