Sandhill 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. (a) What is the beginning retained earnings balance at January 1,2017, if Sandhill prepares comparative financial statements starting in 2017 ? Retained earnings, January 1 $ (b) What is the beginning retained earnings balance at January 1,2020, if Sandhill prepares comparative financial statements starting in 2020 ? Retained earnings, January 1 (c) What is the beginning retained earnings balance at January 1,2021, if Sandhill prepares single-period financial statements for 2021 ? Retained earnings, January 1 (d) What is the net income reported by Sandhill in the 2020 income statement if it prepares comparative financial statements starting with 2018