EXERCISE 6-6 Examining Cost Behaviour and Contribution Margin (L01 - CC1, 3; L02 - CC7; L03 - CC12] Bikes Manufacturing produces and sells children's bikes at an average price of $60. Its costs are as follows: direct materials, $12; direct labour, $7: variable overhead, $3; sales commission, 5% of price. Its fixed monthly costs are $38,000. Required: 1. Using the above cost data, set up a monthly cost equation. 2. What is the company's contribution margin percentage