What was the change in cash, cash equivalents and restricted cash at beginning of year from 2018 to 2019?
{"(in millions of $) -- Net cash provided by/(used in) operating activities": {"2019": 106.5, "2018": 116.7, "2017": -35.1}, "(in millions of $) -- Net cash used in investing activities": {"2019": -264.4, "2018": -202.5, "2017": -419.9}, "(in millions of $) -- Net cash (used in)/provided by financing activities": {"2019": -136.0, "2018": 177.4, "2017": 427.4}, "(in millions of $) -- Net (decrease) increase in cash, cash equivalents and restricted cash": {"2019": -293.9, "2018": 91.6, "2017": -27.5}, "(in millions of $) -- Cash, cash equivalents and restricted cash at beginning of year": {"2019": 704.3, "2018": 612.7, "2017": 640.2}, "(in millions of $) -- Cash, cash equivalents and restricted cash at end of year": {"2019": 410.4, "2018": 704.3, "2017": 612.7}}
cash_2019 = df["(in millions of $) -- Cash, cash equivalents and restricted cash at beginning of year"]["2019"]
cash_2018 = df["(in millions of $) -- Cash, cash equivalents and restricted cash at beginning of year"]["2018"]
answer = cash_2019 - cash_2018