Based upon the following information for Norris Company's electricity costs, use the high-low method to calculate variable electricity costs per kilo-watt hour. Total cost Kilo-watt hours May $8,300 15,000 June 10,400 20,000 July 7,200 12,000 August 9,500 18,000 Select one: a. $0.60 b. $0.52 O c. $0.47 d. $0.40 e. $0.55