What was the change in the amount of Net debt and IFRS 16 lease liabilities from 2018 to 2019?
{"": {"2019": "\u00a3m", "2018": "\u00a3m"}, "Net debt": {"2019": 295.2, "2018": 235.8}, "IFRS 16 lease liabilities": {"2019": 38.9, "2018": "\u2013"}, "Net debt and IFRS 16 lease liabilities": {"2019": 334.1, "2018": 235.8}}
net_debt_2019 = df["Net debt and IFRS 16 lease liabilities"]["2019"]
net_debt_2018 = df["Net debt"]["2018"]
answer = net_debt_2019 - net_debt_2018