It's Still Raining (ISR) manufacturers umbrellas. In order to better budget and manage costs, they are analyzing the purchasing costs behavior. They have the following data from the last six months of last year. Month Total Purchasing Costs Purchase Orders July $19,670 460 August $20,940 560 September $19,430 400 October $20,020 500 November $18,800 470 December $19,340 480 Using the high-low method, calculate the unit variable costs. Please round to two decimal places