d$.$ What is the probability that three or more people are at the coffee urn? $($Do not round intermediate calculations. Round your answer to $1$ decimal place.$)$

Probability $\%$

e$.$ If the cafeteria installs an automatic vendor that dispenses a cup of coffee at a constant time of $15$ seconds, how many customers would you expect to see at the coffee urn $($waiting and$/$or pouring coffee$)?($Round your answer to $2$ decimal places.$)$

Average no of customers

f$.$ If the cafeteria installs an automatic vendor that dispenses a cup of coffee at a constant time of $15$ seconds, how long would you expect it to take $($in minutes$)$ to get a cup of coffee, including waiting time? $($Round your answer to $2$ decimal places.$)$

Expected time minute$($s$)$