Hayes Electronics stocks and sells a particular brand of microcomputer. It costs the firm $450 each time it places an order with the manufacturer for the microcomputers. The cost of carrying one microcomputer in inventory for a year is $170. The store manager estimates that total annual demand for the computers will be 1,200 units, with a constant demand rate throughout the year. Orders are received within minutes after placement from a local warehouse maintained by the manufacturer. The store policy is to never have stockouts of the microcomputers. The store is open for business every day of the year except Christmas Day.

Determine the following:
- Optimal order quantity per order
- Minimum total annual inventory costs
- The optimum number of orders per year
- The optimum time between orders (in working days)