What is the change in Revenue from December 31, 2018 and 2019?
{"": {"2019": "(unaudited) ", "2018": "(unaudited)"}, "Revenue": {"2019": 72576902, "2018": 60249896}, "Income from continuing operations": {"2019": 6912802, "2018": 1559008}}
revenue_2019 = df["Revenue"]["2019"]
revenue_2018 = df["Revenue"]["2018"]
answer = revenue_2019 - revenue_2018