What was the change in the Balance at Beginning of Year between 2017 and 2018?
{"Allowance for doubtful accounts: -- Fiscal 2019": {"Balance at Beginning of Year": 2.2, "Additions Charged to Costs and Expenses": "$\u2014", "Deductions (1)": -0.2, "Balance at End of Year": 2.0}, "Allowance for doubtful accounts: -- Fiscal 2018": {"Balance at Beginning of Year": 2.1, "Additions Charged to Costs and Expenses": 0.2, "Deductions (1)": -0.1, "Balance at End of Year": 2.2}, "Allowance for doubtful accounts: -- Fiscal 2017": {"Balance at Beginning of Year": 2.5, "Additions Charged to Costs and Expenses": 0.2, "Deductions (1)": -0.6, "Balance at End of Year": 2.1}}
balance_2018 = df["Allowance for doubtful accounts: -- Fiscal 2018"]["Balance at Beginning of Year"]
balance_2017 = df["Allowance for doubtful accounts: -- Fiscal 2017"]["Balance at Beginning of Year"]
answer = balance_2018 - balance_2017