probability question

I am having trouble with my stat homework. Maybe someone can give me some guidance? I would really appreciate it!

A woman is fishing for bass on Pinelands pond. Let x=number of 'keepers' that she catches in an hour. The probability distribution for x is given in the table below

x= 0 1 2 3 4 5
p(x)= .1 .2 .3 .2 .1 .1

a) What is the probability that she catches at most 4 keepers?
b) What is the probability that x is greater to and equal to 3?

c) Find Ux, the mean number of keepers caught
d) Find the standard deviation for X, the number of keepers caught
a) the probability of at most 4 is equal to the probability of three or fewer. simply add up the probabilities involved.

b) use the above and adjust for three or greater

some examples:

c) for a probability distribution x= 2 4 6 8 10, P(x)= .1 .3 .1 .2 .3 Ux + 2(.1)+4(.3)+6(.1)+8(.2)+10(.3) = 6.6

d) sigma = sqrt( sum(x-mu)^2*P(x)) so, to begin the pattern for my example in c) = sqrt((2-6.6)^2(.1) + (4-6.6)^2(.3)...)=2.83
okay i calculated it again but came out to 2.01!!! which is the variance.
if i squared the variance (2.01)^2 = 4.0401
would that be the standard deviation??