Derby Phones is considering the introduction of a new model of headphones with the following price and cost characteristics. $ Sales price Variable costs Fixed costs 280 per unit 75 per unit 553,500 per month Required: a. What number must Derby sell per month to break even? b . What number must Derby sell to make an operating profit of $ 225,500 for the month? a. Break-even sales in units b. Number of units to be sold