11 of 15 Dark Ltd makes a single product and has recorded the following costs and production volumes over the past eight months: Month Volume (Units) May 1800 June 3167 July 1700 August 1600 September 1500 October 1300 November 1019 December 1500 Total Cost () 14700 17077 13700 14000 14300 13100 11929 14600 Using high-low method, the estimate variable cost per unit is? (Give your answer to 2 decimal places.)