What was the difference in net cash provided by operating activities in 2019?
{"Net cash provided by operating activities": {"2019": 377.1, "2018": 0.9, "2017": 169.7}, "Net cash (used in) provided by investing activities": {"2019": -710.4, "2018": 506.4, "2017": 272.0}, "Net cash provided by (used in) financing activities": {"2019": 151.9, "2018": -656.6, "2017": -578.3}}
net_cash_2019 = df["Net cash provided by operating activities"]["2019"]
net_cash_2018 = df["Net cash provided by operating activities"]["2018"]
answer = net_cash_2019 - net_cash_2018