Carr Company produces a single product. During the past year, Carr manufactured 29,650 units and sold 24,600 units. Production costs for the year were as follows:

Fixed manufacturing overhead $563,350
Variable manufacturing overhead $243,130
Direct labor $145,285
Direct materials $222,375

Sales totaled $1,070,100, variable selling expenses totaled $140,220, and fixed selling and administrative expenses totaled $210,515. There were no units in beginning inventory. Assume that direct labor is a variable cost.

The contribution margin per unit would be:

I KNOW THE ANSWER IS 17.20 BUT I DONT KNOW WHY! PLEASE GIVE ME A STEP BY STEP EXPLANATION. OVERWISE I WILL NOT RATE! THANK YOU!