Berhannan's Cellular sells phones for $100. The unit variable cost per phone is $50 plus a selling commission of 10%. Fixed manufacturing costs total $1,250 per month, while fixed selling and administrative costs total $2,500. Tax rate is %30. Required: a. What is the contribution margin per phone? b. What is the breakeven point in phones? c. How many phones must be sold to eam pretax income of $7,500? d. How many phones must be sold to earn net income of $7.500