Hi I have a question:

**The number of customers arriving at an office selling tickets for a festival can be modeled by Poisson distribution with mean 1.2 per 2 minute interval. Find the number of arrivals which will not be exceeded in at least 90% of 2 minute intervals.**
I have an idea of how maybe I could answer it. Though it is a guess, so it may be way off:

Because

There will be no more than 3 arrivals in 90% of 2 minute intervals.

Also, as a second question, when I am told

**"A man sells 8 cars a week"**
and am then told to calculate the probability of him selling

**"21 cars in two weeks"**, do I just modify the mean and then work out the probibility? i.e. find the the poisson probability