Exercise 20.3 (Algo) Computing Required Sales Volume (LO20-4, LO20-5) Winchester Manufacturing makes a highly specialized emergency generator for submersible pumping systems. The following information pertains to the company's only product: Required: a. Determine the unit contribution margin. b. Determine the number of units that must be sold each month to break even. c. Determine the number of units that must be sold to earn an operating income of $941,200 per month