A cafeteria serving line has a coffee urn from which customers serve themselves. Arrivals at the urn follow a Poisson distribution at the

rate of $4\mathrm{.}0$ per minute. In serving themselves, customers take about $10$ seconds, exponentially distributed.

a$.$ How many customers would you expect to see, on average, at the coffee urn? $($Do not round intermediate calculations. Round

your answer to $2$ decimal places.$)$

Average no of customers

b$.$ How long would you expect it to take to get a cup of coffee? $($Round your answer to $2$ decimal places.$)$

Expected time

minute$($s

c$.$ What percentage of time is the urn being used? $($Do not round intermediate calculations. Round your answer to $1$ decimal place.$)$

Percentage of time

$\%$

d$.$ What is the probability that three or more people are in the cafeteria? $($Round your intermediate calculations to $3$ decimal places

and final answer to $1$ decimal place.$)$

Probability

$\%$