What was the change in finished goods between 2018 and 2019?
{"Purchased components": {"April 26, 2019": 8, "April 26,2018": 12}, "Finished goods": {"April 26, 2019": 123, "April 26,2018": 110}, "Inventories": {"April 26, 2019": 131, "April 26,2018": 122}}
finished_goods_2019 = df["Finished goods"]["April 26, 2019"]
finished_goods_2018 = df["Finished goods"]["April 26,2018"]
answer = finished_goods_2019 - finished_goods_2018