What is the change in operating income from 2017 to 2018?
{"": {"Fiscal 2018": "", "Fiscal 2017": "(in millions)", "% Change": ""}, "Sales": {"Fiscal 2018": 325.2, "Fiscal 2017": 360.2, "% Change": -10.0}, "Operating income": {"Fiscal 2018": 16.6, "Fiscal 2017": 28.1, "% Change": -41.0}, "Adjusted EBITDA": {"Fiscal 2018": 26.3, "Fiscal 2017": 39.4, "% Change": -33.0}}
operating_income_2018 = df["Operating income"]["Fiscal 2018"]
operating_income_2017 = df["Operating income"]["Fiscal 2017"]
answer = operating_income_2018 - operating_income_2017