Sam Simone is the manager of a family-run pet store. He is deciding whether to open an hour later on Sundays. From past sales on Sundays he has determined that the probability of zero sales during this hour is 20%, one sale is 40%, two sales is 30%, and three sales is 10%. The results are summarized in the following table in the form of a discrete probability distribution.

x ..................P(x)
0 ..................0.2
1 ..................0.4
2 ..................0.3
3 ..................0.1

Compute the mean (the expected number) and the standard deviation of sales for Sam so he can use this information to make an informed decision.