The controller of Cullumber Production has collected the following monthly expense data for analyzing the cost behavior of electricity costs. Total Total Electricity Costs Machine Hours January $2,480 210 February 2,900 340 March 3,520 500 April 4,780 May 3,220 June 5,000 July 4,090 August 3,810 September 5,110 October 4,270 November 3,320 December 5,840 What electricity cost does the cost equation estimate for a level of activity of 500 machine hours? Electricity costs $ By what amount does this differ from March's observed cost for 500 machine hours? Amount differ . $