2021 2020 2019 2018 2017 Sales $ 80,000 $ 66,000 $ 61,000 $ 58,000 $ 50,000 Cost of goods sold 75,000 54,600 42,900 33,300 30,000 Dollar amounts stated are in thousands. a. Compute trend percentages for the above items taken from the financial statements of Lopez Plumbing over a five-year period. Treat 2017 as the base year. b. State whether the trends are favorable or unfavorable.