For question a, your answer is 0.147: Go here:

Poisson Distribution

We know that lambda is the mean, so we need it to equal 4. Enter 10 for n, 0.4 for p, and 2 for k and press enter: Take a look at the entire math work and the answer and let me know if you have questions.

For b, P(x<=2) = P(x=0) + P(x=1) + P(x=2). 0.018 + 0.073 + 0.147 = 0.238. You can use my calculator if you want, or try to do what you did above for question (a) 2 more times for x = 0 and x = 1. Take a look at the formulas on my page and let me know if you have questions.

For c, we know that P(x > 2) = 1 - P(x<=2). So, essentially, it's 1 - your answer for (b). 1 - .238 = 0.762.

Later tonight I'll have the function built on the calculator to calculate cumulative probabilities for questions b and c automatically. I'll PM you or notify you on this thread when that is ready. It will show you the math for each success mentioned above, i.e., P(x=0) + P(x=1) + P(x=2). For now though, try it manually.