In the O'Donnell Manufacturing Company, at an activity level of 80,000 machine hours, total overhead costs were $223,000. Of this amount, utilities were $48,000 (all variable) and depreciation was $60,000 (all fixed). The balance of the overhead cost consisted of maintenance cost (mixed). At 100,000 machine hours, maintenance costs were $130,000.

Assume that all the activity levels mentioned in this problem are within the relevant range.

The variable cost for maintenance per machine hour is?