D6.18 (LO 2, 3, 5) Glacial Springs produces and sells water filtration systems for homeowners. Information regarding its three models is shown below. Basic Basic Plus Premium Total Units sold 840 350 210 1,400 Selling price $250 $400 $800 Variable cost $195 $288 $416 The company's total fixed costs to produce the filtration systems are $140,000. Instructions a. Determine the sales mix as a function of units sold for the three products. b. Determine the weighted-average unit contribution margin. c. Determine the total number of units that the company must sell to break even. d. Determine the number of units of each model that the company must sell to break even.