A survey was conducted to determine the number of cats living in individual households. The results are summarized in the following table:

Number of Cats         Probability

0 …………………     0.37

1 …………………     0.28

2 …………………     0.21

3 …………………     0.10

4 …………………     0.04

a. Determine the mean number of cats per household.

b. Determine the standard deviation for the number of cats per household.