Blue Denim Company makes blue jeans. The company controller wants to use the high-low method to determine what part of electricity costs are fixed and what part are variable. Below is data for the past 8 months. Month Electricity # Machine Cost Hours January $3,255 460 February 3,485 500 March 4,100 600 April 3,300 470 May 3,312 470 June 2,575 350 July 3,910 570 August 4,200 590 Using the high-low method to analyze mixed costs, what is the cost function for electricity costs?