15. Business Tech Services sold 600,000 of their financial spreadsheet mobile phone apps at a price of $3.99 each in 2018. Their major competitor, Online Accounting Services, sold 700,000 financial spreadsheet mobile phone apps at a price of $3.50 each in 2018. In 2019 Business Tech Services kept its price the same, while Online Accounting Services dropped its price to $2.50 each. This caused the sales of Business Tech Services to decline to 450,000. Calculate EXY for these products. Note that while you do not need to show all your work, in order to make full credit you do need to show the correct equation set up in the correct manner.