What was the change in Internally-developed software costs between 2018 and 2019?
{"Internally-developed software costs": {"2019": 345, "2018": 291}, "Payments made to third-party software developers": {"2019": 31, "2018": 38}, "Total software development costs": {"2019": 376, "2018": 329}}
internally_developed_software_costs_2019 = df["Internally-developed software costs"]["2019"]
internally_developed_software_costs_2018 = df["Internally-developed software costs"]["2018"]
answer = internally_developed_software_costs_2019 - internally_developed_software_costs_2018