Compute the Variance and Standard Deviation of a Discrete Random

Compute the Variance and Standard Deviation of a Discrete Random Variable
-A manager at a local company asked his employees how many times they had given blood in the last year. The results of the survey are given below. The random variable x represents the number of times a person gave blood and P(x) represents the probability of selecting an employee who had given blood that percent of the time. What is the standard deviation for the number of times a person gave blood based on this survey $\begin{array}{|c|c|c|c|c|c|c|c|}\hline x & 0 & 1 & 2 & 3 & 4 & 5 & 6 \\\hline P(x) & 0.30 & 0.25 & 0.20 & 0.12 & 0.07 & 0.04 & 0.02 \\\hline\end{array}$

A) $1.54$
B) $1.82$
C) $1.16$
D) $2.23$