Thomas Train has collected the following information over the last six months.

Month_Units producedTotal costs

March_10,000_______$25,600

April____12,000_______26,200

May___20,000_______27,600

June____13,000_______26,450

July___12,000_______26,000

August_15,000_______26,500

Using the high-low method, what is the variable cost per unit?