A key reason for management to build in a margin of safety in its projections is Estes Company sells two types of computer chips. The sales mix is 30% (Chip A) and 70% (Chip B) Cho A has variable costs per unit of $20 and a selling price of $40. Chip B has variable costs per unit of $25 and a selling price of $55. The weighted average unit contribution margin for Estes is