What was the difference in net sales in 2018 between AMER and EMEA regions?
{"Net sales:     -- AMER ": {"2019": 1429.3, "2018": 1218.9}, "Net sales:     -- APAC ": {"2019": 1557.2, "2018": 1498.0}, "Net sales:     -- EMEA ": {"2019": 309.9, "2018": 281.5}, "Net sales:     -- Elimination of inter-segment sales": {"2019": -132.0, "2018": -124.9}, "Net sales:     -- Total net sales": {"2019": 3164.4, "2018": 2873.5}}
net_sales_amer_2018 = df["Net sales:     -- AMER "]["2018"]
net_sales_emea_2018 = df["Net sales:     -- EMEA "]["2018"]
answer = net_sales_amer_2018 - net_sales_emea_2018