The Kentucky Tools Machine Shop wants to develop a cost estimating equation for its monthly cost of electricity. It has the following data: Month Cost of Electricity (Y) Direct Labor-Hours (X) January $12,600 750 April $13,500 850 July $15,300 1,000 October $13,050 800 What would be the best equation using the high-low method? Select one: a. Y = $4,500 + $10.80X b. Y = $900 + $10.80X c. Y = $2,700 + $14.40X d. Y = $3,600 + $7.20X