Scherer Corporation is preparing a bid for a special order that would require 720 liters of U48N material. The company already has 560 liters of this raw material in stock, which originally cost $6.30 per liter. The U48N material is used in the company's core product and is regularly replenished. The resale value of the existing stock of the material is $5.80 per liter. New stock of the material can be easily purchased for $6.65 per liter. 

What is the relevant cost of the 720 liters of raw material when deciding how much to bid on the special order?