The manager of large computer network has developed following probability distribution of number of interruptions for each day.
Interruptions (X)

P (X)

0

0.32

1

0.35

2

0.18

3

0.08

4

0.04

5

0.02

6

0.01

Total

1

a. Evaluate the expected number of interruptions per day
b. Evaluate the standard deviation.