What was the percentage change in gross profit in 2018 from 2017?
{"Net sales": {"2018": 2157.7, "2017": 1797.6}, "Less: surcharge revenue": {"2018": 365.4, "2017": 239.2}, "Net sales excluding surcharge revenue": {"2018": 1792.3, "2017": 1558.4}, "Gross profit": {"2018": 382.3, "2017": 300.8}, "Gross margin": {"2018": 17.7, "2017": 16.7}, "Gross margin excluding surcharge revenue": {"2018": 21.3, "2017": 19.3}}
gross_profit_2018 = df["Gross profit"]["2018"]
gross_profit_2017 = df["Gross profit"]["2017"]
answer = (gross_profit_2018 - gross_profit_2017) / gross_profit_2017 * 100.0