Peppers Lockdown produces keys for homes and cars. As Peppers is planning for next year's production, he decided to implement a high-low system to forecast future costs. With total production of 2,500,000 keys at a total cost of $10,000, in 2009, and total production of 3,000,000 keys at a total cost of $20,000 in 2010 what is the variable cost per key?