Taran Company incurred the following costs for the months of January and February.

Type of Cost	January	February
Insurance	5000	5000
Utilities	4000	6000
Depreciation	3500	3500
Materials	10000	20000

Assume that output was 5000 units in January and 10000 units in February, utility cost is a mixed cost, and the fixed cost of utilities was 3000. What was the variable rate per unit of output for utilities cost?