What is the increase/ (decrease) in Capitalized costs to obtain a contract from 2018 to 2019
{"($ in millions) -- At December 31:": {"2019": 2019, "2018": 2018}, "($ in millions) -- Capitalized costs to obtain a contract": {"2019": 609, "2018": 717}, "Deferred costs to fulfill a contract -- Deferred setup costs": {"2019": 1939, "2018": 2085}, "Deferred costs to fulfill a contract -- Other deferred fulfillment costs": {"2019": 1820, "2018": 2173}, "Deferred costs to fulfill a contract -- Total deferred costs (1)": {"2019": 4368, "2018": 4975}}
capitalized_costs_2019 = df["($ in millions) -- Capitalized costs to obtain a contract"]["2019"]
capitalized_costs_2018 = df["($ in millions) -- Capitalized costs to obtain a contract"]["2018"]
answer = capitalized_costs_2019 - capitalized_costs_2018