The controller of Cullumber Industries has collected the following monthly cost data for use in analyzing the behavior of maintenance costs. Month Total Maintenance Costs Total Machine Hours January $2,630 340 February 2,930 390 March 3,530 540 April 4,430 650 May 3,130 540 June 5,030 740 (a1) Determine the unit variable costs using the high-low method for this mixed cost. (Round answer to 2 decimal places e.g. 2.25.) Variable cost per machine hour $