Santucci Appliances received an invoice dated November $16$ with terms $3/10$ E$.$O$.$M$.$ for the items listed below.

$5$ refrigerators at $$990$ each less $25\%$ and $6\%$

$4$ dishwashers at $$666$ each less $15\frac{1}{3}\%,12\mathrm{.}5\%,$ and $4\%$

$($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?

$($c$)$ What is the amount of the cash discount if a partial payment is made such that a balance of $$2500$ remains outstanding on the invoice?