Use the following information for Question $28$ & $29$:

A grocery store uses $600$ boxes of plastic bags per month. The boxes cost $$50$ each, placing an order for plastic bags costs $$30,$ and holding costs are $$10$ per box per month.

What is the economic order quantity?

A$.$

$120$

B$.$

$40$

C$.$

$200$

D$.$

$60$

E$.$

$80$