Bay Street Vending received an invoice dated June $18$ with terms $3/15,$ n$/30.$ The amount stated on the invoice was $$3861\mathrm{.}00$

$($a$)$ What is the last day for taking the cash discount?

$($b$)$ What is the amount due if the invoice is paid on the last day for taking the discount?

$($a$)$ The last day to take the cash discount is

$($b$)$ The amount due is $

$($Round to the nearest cent as needed.$)$