Skippy Quadcopters plans to sell a standard quadcopter (toy drone) for $60 and a deluxe quadcopter for $90. Skippy purchases the standard quadcopter for $50 and the deluxe quadcopter for $65. Management expects to sell two deluxe quadcopters for every three standard quadcopters. The company's monthly fixed expenses are $17,600. How many of each type of quadcopter must Skippy sell monthly to breakeven? To earn $11,200? First identify the formula to compute the sales in units at various levels of operating income using the contribution margin approach. (Abbreviations used: Avg. = average, and CM = contribution margin.) = Breakeven sales in units