Audio produces stereo equipment. The Oz Audio Vector 12 inch subwoofer with 700 watts max power, vapor deposition cone and lighted LED logo sells at the suggested retail price of about $70.00. Variable costs involved in producing the subwoofers are $26.25. Fixed costs are estimated at $4,375. Oz, who sells direct to retailers, intends to give retailers a margin of 40 percent off the suggested retail price. What is the contribution per unit for Oz