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.

Required:

a. What is the contribution margin per phone?

b. What is the break-even point in phones?

c. How many phones must be sold to earn pre-tax income of $7,500?