CPG Company manufactures chemicals. Chemical agent PL62 is refined in the Refining Department and, after it is transferred to the Mixing department, a reactive agent is added to it,. In January, 6,000 gallons of PL 62 having a cost of $30,000 were transferred from the refining to the Mixing department where 4,000 gallons of the reactive agent were added to it. When calculating the inventory costs in the Mixing department, what will the cost per unit relating to gallons transferred in from the Refining department be?