What is the percentage change in net inventories from 2018 to 2019?
{"Finished products": {"2019": 10905, "2018": 7099}, "Work in process and inventoried costs under long-term contracts": {"2019": 46951, "2018": 63169}, "Materials and purchased parts": {"2019": 48938, "2018": 23710}, "Customer advances": {"2019": "\u2014", "2018": -9779}, "Net inventories": {"2019": 106794, "2018": 84199}}
net_inventories_2019 = df["Net inventories"]["2019"]
net_inventories_2018 = df["Net inventories"]["2018"]
answer = ( net_inventories_2019 - net_inventories_2018 ) / net_inventories_2018 * 100.0