A cellular company purchased $$28,600$ in cell phones on September $25.$ The terms of sale were $\frac{4}{20},\frac{3}{30},\frac{n}{60}.$ Freight terms were F$.$O$.$B$.$ destination. Returned goods amounted to $$650.$

$($a$)$ What is the net amount due $($in $ $)$ if the cellular company sends the manufacturer a partial payment of $$4,000$ on October $20?($Round your answer to the nearest cent.$)$

$

$($b$)$ What is the net date?

$($c$)$ If the manufacturer charges a $4\frac{1}{2}\%$ late fee, how much $($in $$)$ would the cellular company owe if it did not pay the balance by the net dater $($Round your answer to the neares

$