In a forest, the probability that a randomly sampled tree is oak is

In a forest, the probability that a randomly sampled tree is oak is 0.1, pine 0.3, maple 0.35 and 0.25 is the probability that a randomly sampled tree is of any other type. If 8 trees are sampled randomly from a forest 

(Hint: You may also think of the problem as probability of a tree being oak is 0.1 and non-oak is 0.9).

a) (6 pts) What is the probability that 2 of the 8 trees sampled is oak?

P(Y=8)= 8!/(2!(8-2)!(.1)^2(1-.1)^6=.1488
Binomial with n = 8 and p = 0.1

x P( X = x )
1 0.382638
2 0.148803
3 0.033067
4 0.004593
5 0.000408
6 0.000023
7 0.000001
8 0.000000

b) (6 pts) What is the probability that at least one of the 8 trees sampled is either an oak or a pine?

c) (5 pts) Let Y be a random variable denoting the number of maple trees in the sample of 8. What is the expected value of Y (mean value of Y)? If this value is not a whole number, will you round it up to a whole number? 

d) (3 pts) What is the standard deviation of Y?