The controller of Hall Industries has collected the following monthly cost data for use in analyzing the behavior of maintenance costs.

$\backslash$table$[[$Month$,\backslash$table$[[$Total$],[$Maintenance Costs$]],\backslash$table$[[$Total$],[$Mashine Hours$]]],[$January$,$$$2,640,3,500],[$February$,3,000,4,000],[$March$,3,600,6,000],[$April$,4,500,7\mathrm{.}900],[$May$.,3,200,5,000],[$June:$,4,620,8,000]]$

$($a$1)$

Determine the unit variable costs using the high$-$low method for this mixed cost. $($Round answar to $2$ decimal places eg$.225.)$

Variable cost per machine hour

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