Please assist in explaining how to solve this problem.

Assume the Zeus Furniture Company sells two kinds of picnic tables, pine and redwood. At a 4:1 unit sales mix in which Midwest sells four pine tables for every redwood table, the following revenue and cost information is available. Pine Table Redwood Table Unit selling price $200 $600 Unit variable costs $125 $ 275 Unit contribution margin $75 $ 325 Fixed costs per month: $18,150 Required: Assuming a 4:1 sales mix: a) Calculate Zeus Furniture's current monthly average unit contribution margin. b ) Break-even sales volume. c) Number of units of Pine and Redwood tables at break-even point. d) Describe what the effect a change in the sales-mix would have on contribution margin