Solve the questions $8,9$ and $10$&$11$ by using following

data

It is known that $20$ percent of new hiring employees change their jobs in the first year.

Assuming that this claim is true, and Let $x$ represents the number of employees who change his jobs in the first year. A random sample of $15$ is selected use Table of

Binomial in "Statistical Tables" to solve the following questions

$7$

Find the mean of $x$

$8$

$3$

$10$