Leilani Lavender's law office has traditionally ordered ink refills $60$ units at a time. The firm estimates that carrying cost is $40\%$ of the $$10\mathrm{.}00$ un cost and that annual demand is about $240$ units per year. The assumptions of the basic EOQ model are thought to apply.

a$)$ For what value of ordering cost would its action be optimal?

Its action would be optimal given an ordering cost of $ $($round your response to two decimal places$).$ per order