The controller of Cullumber Production has collected the following monthly expense data for analyzing the cost behavior of electricity costs. January February March April May June July August September October November December Total Total Electricity Costs Machine Hours $2,700 290 2,980 350 3,590 480 4,620 690 3,160 460 5,000 780 4,110 620 3,910 510 5,120 680 4,200 620 3,200 350 7,290 800 (a) Determine the fixed- and variable-cost components using the high-low method. Fixed-costst 4 Variable-costs (b) What electricity cost does the cost equation estimate for a level of activity of 480 machine hours? Electricity costs By what amount does this differ from March's observed cost for 480 machine hours? Amount differ $ (C) What electricity cost does the cost equation estimate for a level of activity of 780 machine hours? Electricity costs By what amount does this differ from June's observed cost for 780 machine hours? Amount differs