Below is a probability distribution

x	Probability f (x)
0	0.10
1	0.14
2	?
3	0.22
4	0.15
5	0.08

Calculate and answer:

a) Find P(4). (2 points)

b) What is the expected value (mean) of the number of services? (3 points)

c) What is the variance of the number of services?(3 points)

d) What is the standard deviation?(2 points)