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Below is the net income of Sweet Instrument Co., a private corporation, computed under the three inventory methods using a periodic system. a) Assume that in 2018 Sweet decided to change from the FIFO method to the average-cost method of pricing inventories. Prepare the journal entry necessary for the change that took place during 2018, and show net income reported for 2015, 2016, 2017, and 2018. (Credit account titles are automatically indented when amount is entered. Do not indent manually. If no entry is required, select "No Entry'' for the account titles and enter 0 for the amounts.) (b) Assume that in 2018 Sweet, which had been using the LIFO method since incorporation in 2015, changed to the FIFO method of pricing inventories. Prepare the journal entry necessary to record the change in 2018 and show net income reported for 2015, 2016, 2017, and 2018. (Credit account titles are automatically indented when amount is entered. Do not indent manually. If no entry is required, select "No Entry" for the account titles and enter 0 for the amounts.)