What was the percentage change in Net sales between Three Months Ended  September and December in 2019?
{"Net sales": {"March 31, 2019": 143791.0, "June 30, 2019": 156391.0, "September 30, 2019": 114092.0, "December 31, 2019": 115787.0}, "Gross profit": {"March 31, 2019": 60612.0, "June 30, 2019": 65015.0, "September 30, 2019": 46331.0, "December 31, 2019": 47209.0}, "Operating income (loss)": {"March 31, 2019": -6167.0, "June 30, 2019": 562.0, "September 30, 2019": -20288.0, "December 31, 2019": -14070.0}, "Net income (loss)": {"March 31, 2019": 770.0, "June 30, 2019": 3995.0, "September 30, 2019": -46123.0, "December 31, 2019": -11624.0}, "Earnings (loss) per common share - basic": {"March 31, 2019": 0.02, "June 30, 2019": 0.08, "September 30, 2019": -0.96, "December 31, 2019": -0.25}, "Earnings (loss) per common share - diluted": {"March 31, 2019": 0.02, "June 30, 2019": 0.08, "September 30, 2019": -0.96, "December 31, 2019": -0.25}}
net_sales_2019 = df["Net sales"]["December 31, 2019"]
net_sales_2019_sep = df["Net sales"]["September 30, 2019"]
answer = (net_sales_2019 - net_sales_2019_sep) / net_sales_2019_sep * 100.0