Please show work to understand how to do this.

Buffalo Industries uses a perpetual inventory system. Data for product E2-D2 includes the following purchases. Date Number of Units Unit Price 40 $14 May 7 July 28 30 19 On June 1, Buffalo sold 20 units, and on August 27, 30 more units. (a) X Your answer is incorrect. Calculate the average cost of the goods sold in the sale. (Round answers to 3 decimal places, eg. 5.125.) June 1 sale: $ 280. Aug. 27 sale: $ 510