What was the percentage change in total revenue from 2018 to 2019?
{"Revenues from fixed rate time charters": {"2017": 485961, "2018": 515324, "2019": 558266}, "Revenues from variable rate time charters": {"2017": "\u2014", "2018": "\u2014", "2019": 64334}, "Revenues from The Cool Pool Limited (GasLog vessels)": {"2017": 38046, "2018": 102253, "2019": 45253}, "Revenues from vessel management services": {"2017": 1222, "2018": 767, "2019": 784}, "Total": {"2017": 525229, "2018": 618344, "2019": 668637}}
total_2019 = df["Total"]["2019"]
total_2018 = df["Total"]["2018"]
answer = ( total_2019 - total_2018 ) / total_2018 * 100.0