To lower its corporate income tax, accountants of a large company depreciated a word processing system over several years using a linear model, as shown in the worksheet below. Tax Worksheet Method of depreciation: Linear Property Years after purchase Value Word processing system 2 $68,500 " 4 $39,000 (a) Use the information in the worksheet to write a linear equation relating the years since the system was purchased x and its value y, in dollars.