Understanding the Power Function for Poisson Distribution

[Artusartos]

In this link:

http://www.math.harvard.edu/~phorn/362/362assn3-solns.pdf

I do not understand how they got the power function for number 5...can anybody explain it to me please?

Thanks in advance

 

[haruspex]

You understand that Y ~ Poisson(12θ)? Given that, what are the probabilities for Y being 0, 1, 2?

 

[Artusartos]

You understand that Y ~ Poisson(12θ)? Given that, what are the probabilities for Y being 0, 1, 2?

Oh, ok thanks.