$3$

$67$

$8$

$9$

To be able to go on a trip to South America, Lashonda decides to save for $4$ years. She opens a savings account with $$400.$ The account pays simple interest at an annual rate of $4\%.$ She doesn't make any more deposits.

Answer the following questions. If necessary, refer to the list of financial formulas.

$($a$)$ How much total interest will Lashonda earn?

$$$

$($b$)$ What will the total amount in the account be $($including interest$)?$

$$$