What is the percentage increase in sales and marketing expenses from 2017 to 2019?
{"": {"2019": "", "2018": "", "2017": "(In thousands, except percentages)", "2018 to 2019 % change": "", "2017 to 2018 % change": ""}, "Sales and Marketing": {"2019": 396514, "2018": 291668, "2017": 211918, "2018 to 2019 % change": 36, "2017 to 2018 % change": 38}}
sales_2019 = df["Sales and Marketing"]["2019"]
sales_2017 = df["Sales and Marketing"]["2017"]
answer = (sales_2019 - sales_2017) / sales_2017 * 100.0