Rally Quadcopters plans to sell a standard quadcopter (toy drone) for $60 and a deluxe quadcopter for $90. Rally purchases the standard quadcopter for $40 and the deluxe quadcopter for $70. Management expects to sell two deluxe quadcopters for every three standard quadcopters. The company's monthly fixed expenses are $21,000. How many of each type of quadcopter must Rally sell monthly to breakeven? To earn $14,000? 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.) ( Fixed expenses + Operating income )/ Weighed-avg. CM per unit = Breakeven sales in units