Alex Appliance Center sells $150$ refrigerators per year. It costs $$20$ to place an order, and it costs an average of $$15$ annually to carry one refrigerator in inventory. It takes about $30$ business days from the time Alex Appliance Center places an order until the refrigerators are received. Alex is open for business $300$ days per year. Calculate Alex's Economic Order Quantity. $($Do not round until your final answer. Round your final answer to the nearest whole number.$)$