At the end of the $1$st Quarter, To Your Health Medical Center had $$900$ million in accounts receivable on the balance sheet. During the $1$st Quarter, Your Health generated $$6,000$ million in sales revenue. Given there are $90$ days in the $1$ st Quarter, what was the average collection period $($ACP$)?$

$13\mathrm{.}5$ days

$600$ days

$56\mathrm{.}7$ days

$51\mathrm{.}9$ days