Nutt Industries electricity costs and machine hours over a six-month period follow:

	Machine Hours	Electricity Cost
January	2,000	$4,800
February	2,500	5,200
March	3,000	5,400
April	2,400	5,000
May	2,800	5,600
June	2,200	5,000

Using the high-low method, what is the formula that can be used to estimate electricity costs at different levels of volume?

a.	Electricity costs = $2,800 + ($1.00 x number of machine hours)
b.	Electricity costs = $2,600 + ($1.00 x number of machine hours)
c.	Electricity costs = $400 + ($1.67 x number of machine hours)
d.	Electricity costs = $3,600 + ($.60 x number of machine hours)