What was the change in net income in First Quarter in 2019 from 2018?
{"Fiscal Year 2019 -- Net sales": {"First Quarter": 572.4, "Second Quarter": 556.5, "Third Quarter": 609.9, "Fourth Quarter": 641.4}, "Fiscal Year 2019 -- Gross profit": {"First Quarter": 91.7, "Second Quarter": 107.0, "Third Quarter": 123.2, "Fourth Quarter": 122.9}, "Fiscal Year 2019 -- Operating income": {"First Quarter": 45.0, "Second Quarter": 55.4, "Third Quarter": 73.2, "Fourth Quarter": 67.9}, "Fiscal Year 2019 -- Net income": {"First Quarter": 31.5, "Second Quarter": 35.5, "Third Quarter": 51.1, "Fourth Quarter": 48.9}, "Fiscal Year 2018 -- Net sales": {"First Quarter": 479.8, "Second Quarter": 487.8, "Third Quarter": 572.2, "Fourth Quarter": 618.0}, "Fiscal Year 2018 -- Gross profit": {"First Quarter": 85.6, "Second Quarter": 85.7, "Third Quarter": 96.1, "Fourth Quarter": 114.9}, "Fiscal Year 2018 -- Operating income": {"First Quarter": 42.2, "Second Quarter": 41.4, "Third Quarter": 45.7, "Fourth Quarter": 60.0}, "Fiscal Year 2018 -- Net income": {"First Quarter": 23.4, "Second Quarter": 92.1, "Third Quarter": 30.2, "Fourth Quarter": 42.8}}
net_income_2019_first_quarter = df["Fiscal Year 2019 -- Net income"]["First Quarter"]
net_income_2018_first_quarter = df["Fiscal Year 2018 -- Net income"]["First Quarter"]
answer = net_income_2019_first_quarter - net_income_2018_first_quarter