Problem: Emma sells motherboards for personal computers. For quantities up through 25, she charges $350 per board; for quantities between 26 and 50, she charges $315 for each board purchased beyond 25; and she charges $285 each for the additional quantities over 50. A large communication firm expects to require these motherboards for the next years at a rate of at least 140 per year. Order setup costs are $30, and holding costs are based on an 18 percent annual interest rate. What should be the best ordering quantity and what is the minimum average total cost per year?