Need help with stats (3)!

Hi everybody,

i would first like to apologise, in case i am posting this under the wrong section, as i am a new member. I am in need of help of some stats questions, please help me by providing answers and if possible, some explanation to it.

Thank you all!

8. The number of requests for assistance received by a towing service is a Poisson

process with rate =4 per hour.

a) What is the probability that exactly 10 requests are received during a particular

2-hour period?

b) If the operators of the towing service took a 30-minute break for lunch, what

is the probability that they do not miss any calls for assistance?

c) How many calls would you expect during their break?

9. A busy restaurant determined that between 6.30 pm and 9.00 pm on Friday nights,

the arrivals of customers are Poisson distributed with an average arrival rate of 3 per

minute.

a) What is the probability that at least 2 minutes will elapse between arrivals?

b) What is the expected amount of time between arrivals? Its standard deviation?