The controller of Cullumber Production has collected the following monthly cost data for analyzing the behavior of electricity costs. Total Total Electricity Costs Machine Hours January $2,700 190 February 2.980 350 March 3,590 480 April 4,620 690 May 3,160 460 June 5,000 780 July 4,110 620 August 3,910 510 September 5,120 680 October 4,200 620 November 3,200 350 December 7,290 800 (a) Your answer is correct. Determine the fixed costs and unit variable costs using the high-low method. Total fixed costs 90 Variable cost per machine hour $(b) What electricity cost does the cost equation estimate for a level of activity of 480 machine hours? Electricity cost By what amount does this differ from March's observed cost for 480 machine hours? Amount differ