The following information is available for a company's utility cost for operating its machines over the last four months.

Month	Machine hours		Utility cost
January	900		$	5,450
February	1,800		$	6,900
March	2,400		$	8,100
April	600		$	3,600

Using the high-low method, the estimated variable cost per machine hour for utilities is:

$3.38

$6.00

$6.17

$4.22

$2.50