What is the percentage change in cash and cash equivalents in 2018 compared to 2015?
{"Operations data: -- Net revenues": {"2019(1)(8)": 5366.8, "2018(2)": 5191.2, "2017(3)": 4607.5, "2016(4)": 3789.9, "2015(5)": 3582.4}, "Operations data: -- Gross profit": {"2019(1)(8)": 3427.1, "2018(2)": 3279.5, "2017(3)": 2864.8, "2016(4)": 2332.4, "2015(5)": 2164.6}, "Operations data: -- Income from operations": {"2019(1)(8)": 1498.4, "2018(2)": 1396.4, "2017(3)": 1210.2, "2016(4)": 1054.6, "2015(5)": 1027.9}, "Operations data: -- Net earnings(6)": {"2019(1)(8)": 1767.9, "2018(2)": 944.4, "2017(3)": 971.8, "2016(4)": 658.6, "2015(5)": 696.1}, "Per share data: -- Basic earnings per share": {"2019(1)(8)": 17.02, "2018(2)": 9.15, "2017(3)": 9.51, "2016(4)": 6.5, "2015(5)": 6.92}, "Per share data: -- Diluted earnings per share": {"2019(1)(8)": 16.82, "2018(2)": 9.05, "2017(3)": 9.39, "2016(4)": 6.43, "2015(5)": 6.85}, "Per share data: -- Dividends declared per share": {"2019(1)(8)": 1.9, "2018(2)": 1.7, "2017(3)": 1.4625, "2016(4)": 1.25, "2015(5)": 1.05}, "Balance sheet data: -- Cash and cash equivalents": {"2019(1)(8)": 709.7, "2018(2)": 364.4, "2017(3)": 671.3, "2016(4)": 757.2, "2015(5)": 778.5}, "Balance sheet data: -- Working capital(7)": {"2019(1)(8)": -505.4, "2018(2)": -200.4, "2017(3)": -140.4, "2016(4)": -25.0, "2015(5)": 126.2}, "Balance sheet data: -- Total assets": {"2019(1)(8)": 18108.9, "2018(2)": 15249.5, "2017(3)": 14316.4, "2016(4)": 14324.9, "2015(5)": 10168.4}, "Balance sheet data: -- Current portion of long-term debt": {"2019(1)(8)": 602.2, "2018(2)": 1.5, "2017(3)": 800.9, "2016(4)": 401.0, "2015(5)": 6.8}, "Balance sheet data: -- Long-term debt, net of current portion": {"2019(1)(8)": 4673.1, "2018(2)": 4940.2, "2017(3)": 4354.6, "2016(4)": 5808.6, "2015(5)": 3264.4}, "Balance sheet data: -- Stockholders equity": {"2019(1)(8)": 9491.9, "2018(2)": 7738.5, "2017(3)": 6863.6, "2016(4)": 5788.9, "2015(5)": 5298.9}}
cash_2018 = df["Balance sheet data: -- Cash and cash equivalents"]["2018(2)"]
cash_2015 = df["Balance sheet data: -- Cash and cash equivalents"]["2015(5)"]
answer = (cash_2018 - cash_2015) / cash_2015 * 100.0