Used car dealerships generally have sales quotas that they strive to hit each month, quarter, and calendar year. Consequently, buying a used car toward the end of those periods presents a great opportunity to get a good deal on the car. A local dealership has compiled monthly sales data for used cars (Cars) from 2014-2019, a portion of which is shown in the accompanying table. Bpictureclick here for the Excel Data File a. Estimate the linear regression models using seasonal dummy variables with and without the trend term. Which is the preferred model? (Negative values for regression coefficients should be indicated by a minus sign; round your answer to 2 decimal places.) b. Use the preferred model to forecast sales for used cars in the first two months of 2020 . (Round coefficient estimates to at least 4 decimal places and final answers to 2 decimal places.) Used car dealerships generally have sales quotas that they strive to hit each month, quarter, and calendar year. Consequently, buying a used car toward the end of those periods presents a great opportunity to get a good deal on the car. A local dealership has compiled monthly sales data for used cars (Cars) from 2014-2019, a portion of which is shown in the accompanying table. Bpictureclick here for the Excel Data File a. Estimate the linear regression models using seasonal dummy variables with and without the trend term. Which is the preferred model? (Negative values for regression coefficients should be indicated by a minus sign; round your answer to 2 decimal places.) b. Use the preferred model to forecast sales for used cars in the first two months of 2020 . (Round coefficient estimates to at least 4 decimal places and final answers to 2 decimal places.)