What was the increase / (decrease) in the current assets from 2018 to 2019?
{"($ in millions) -- At December 31:": {"2019": 2019.0, "2018": 2018.0}, "($ in millions) -- Current assets": {"2019": 38420.0, "2018": 49146.0}, "($ in millions) -- Current liabilities": {"2019": 37701.0, "2018": 38227.0}, "($ in millions) -- Working capital": {"2019": 718.0, "2018": 10918.0}, "($ in millions) -- Current ratio": {"2019": 1.02, "2018": 1.29}}
dollars_in_millions__Current_assets_2019 = df["($ in millions) -- Current assets"]["2019"]
dollars_in_millions__Current_assets_2018 = df["($ in millions) -- Current assets"]["2018"]
answer = dollars_in_millions__Current_assets_2019 - dollars_in_millions__Current_assets_2018