A consumer protection agency's consumer response team accepts complaints related to mortgages, bank accounts

and services, private student loans, other consumer loans, and credit reporting. Of the customers who registered a

bank account and service complaint, $20\%$ cited "deposit and withdrawal" as the type of complaint. Consider a sample

of $20$ consumers who registered bank account and service complaints. Use the binomial model to complete parts $($a$)$

through $($e$)$ below.

a$.$ What is the expected value, or mean, of the binomial distribution?

The expected value is

$($Type an integer or a decimal. Do not round.$)$