ignore my answers! please help me work out c & d im having trouble!

5. The New Age Pet Store sells Diva Doggie pet waste disposal systems for $50 each. The systems include the unit and a one-year supply of enzyme digester waste terminator. The cost of the unit and enzyme is $35. The only other costs are fixed costs of $3,000. During the current period, New Age sold 600 of the units through the store's new on-line catalog division. Required: a. What is the contribution margin per unit? 15 b. What is the contribution margin ratio? 30'). c. What is the breakeven point in units? In dollars? 200, 3000 d. What is the margin of safety in units? In dollars? 200, 20,000