The following table shows part of the probability distribution for a random variable x.

x	f(x)
0	0.3
1	?
2	0.2
3	?
4	0.15

(a)The mean of the above distribution is known to be 1.75 (i.e.,

E(x) = 1.75).

Determine f(1) and f(3).

f(1)=

f(3)=

(b)Compute the variance and the standard deviation for the above probability distribution. (Round your standard deviation to three decimal places.)

variance?

standard deviation?