Harlan Gravity Grips produces spike sets for track shoes. CEO Brittany Harlan has gathered the following information about the company's sales volume and marketing cost for the past six months: Sales Volume Total Marketing Costs January 64.500 $8.265 February 48.400 $6,605 + March 69.800 $8,420 April 74,600 $8.635 May 67.300 $8.180 June 76.900 $8.885 (a ) (b) (c) Represent the marketing cost function in equation form. (Round variable cost to 2 decimal places, eg. 15.25 and other answer to o deemial places, eg. 5,275) Marketing cost function - $ x sets sold + S