Sheffield Company started operations on January 1, 2015, and has used the FIFO method of inventory valuation since its inception. In 2021, it decides to switch to the average-cost method. You are provided with the following information. Retained Earnings (Ending Balance) Net Income Under FIFO Under Average-Cost Under FIFO 2015 $108,100 $97,500 $91,300 2016 64,700 60,000 157,900 2017 89,200 80,000 239,300 2018 125,700 136,100 332.400 2019 323,100 312,200 648,700 2020 310,200 315,500 843,200 (a) What is the beginning retained earnings balance at January 1. 2017, if Sheffield prepares comparative financial statements starting in 2017? Retained earnings, January 1 $ (b) What is the beginning retained earnings balance at January 1, 2020, if Sheffield prepares comparative financial statements starting in 2020? Retained earnings, January 1 $ (c) What is the beginning retained earnings balance at January 1, 2021. if Sheffield prepares single-period financial statements for 2021 Retained earnings, January 1