What was the percentage change in total net sales between 2018 and 2019?
{"Product and service revenue recognized at point in time": {"2019": 786918, "2018": 715055, "2017": 667440}, "Extended warranty and service contracts recognized over time": {"2019": 2030, "2018": 3837, "2017": 3572}, "Total": {"2019": 788948, "2018": 718892, "2017": 671012}}
total_2019 = df["Total"]["2019"]
total_2018 = df["Total"]["2018"]
answer = ( total_2019 - total_2018 ) / total_2018 * 100.0