What was the percentage change in the free cash flow from FY18 to FY19?
{"Free Cash Flow": {"FY19 m": 54.9, "FY18 m": 92.4, "Change (As reported)": 37.5}, "Net Debt": {"FY19 m": 288.5, "FY18 m": 501.1, "Change (As reported)": ""}, "Net Debt:EBITDA as per financing agreements": {"FY19 m": 1.8, "FY18 m": 2.3, "Change (As reported)": ""}, "ROIC": {"FY19 m": 14.4, "FY18 m": 15.6, "Change (As reported)": -120.0}}
free_cash_flow_2019 = df["Free Cash Flow"]["FY19 m"]
free_cash_flow_2018 = df["Free Cash Flow"]["FY18 m"]
answer = ( free_cash_flow_2019 - free_cash_flow_2018 ) / free_cash_flow_2018 * 100.0