Consider the following data for Magnimus Corporation.

JulyAugustSeptemberSales in units 4,300 4,800 5,400 Sales revenue$430,000 $480,000 $540,000 Direct materials 78,260 87,360 98,280 Direct labour 95,460 106,560 119,880 Manufacturing overhead 61,230 65,730 71,130 Sales commission 34,400 38,400 43,200 Other selling expenses 39,970 41,970 44,370 Administrative expenses 32,300 32,300 32,300

Required: Write the cost equation for sales commission. (Round your answer to 2 decimal places.)