27. ABC Company sells three products with exactly the same price of $20 a unit. However, As variable cost is at 40%, Bs at 50%, and Cs at 60%. Fixed costs amount to $18,000. An additional $9,000 needs to be spent on advertising to boost sales. Sales mix is at 500, 1,500, and 3,000 units for A, B, and C respectively. Sales in dollars for C at breakeven amounts to?

1. $18,000
2. $24,000
3. $36,000
4. $45,000

The correct answer is c. ($36,000) but I do not understand how this is calculated.