Three university students decided to operate an on-campus business producing and selling novelty t-shirts that also promoted their university name. They were able to secure the use of a room in one of the campus buildings for a charge of $800.00 total for the school year. The students decided that they each wanted $2000 income for the year for operating the business. Advertising and promotion costs were estimated at $400 for the year. They decided that the selling price for the t-shirts would be $12.00, and their best estimate of required sales to break even was 1800 shirts.

A) What was the variable cost per unit? ($8)

B) What was the contribution margin? ($4)

C) What was the margin as a percentage of the sales? (33.3%)

D) What was the margin as a percentage of the cost? (50%)

Please show me the solutions step by step, thank you.