A retail store imports an enterprise model solid-state drive (SSD) at a fixed price of $200 per unit from the sole distributer of the SSD. The store received an offer of 15% discount on orders of 80 or more units. The estimated sales for the year are 300 units, the cost incurred per order is $100 and the average holding cost per unit per annum is estimated to be $6 per unit. Decide the optimal quantity for the store to buy in each order (round up to the nearest integer).