What is the change in total research and development expenses from 2018 to 2019?
{"Year ended December 31, -- (EUR million)": {"2018": 2018.0, "2019": 2019, "% Change": "% Change"}, "Front-end: -- Research and development expenses": {"2018": 125.3, "2019": 150.7, "% Change": 20.0}, "Front-end: -- Capitalization of development expenses": {"2018": -49.7, "2019": -60.2, "% Change": 21.0}, "Front-end: -- Research and development grants and credits": {"2018": -0.3, "2019": "\u2013", "% Change": "\u2013"}, "Front-end: -- Amortization of capitalized development  expenses": {"2018": 12.0, "2019": 15.6, "% Change": 30.0}, "Front-end: -- ": {"2018": 87.3, "2019": 106.1, "% Change": 22.0}, "Front-end: -- Impairment capitalized development expenses": {"2018": 1.3, "2019": 4.8, "% Change": "\u2013"}, "Front-end: -- Total": {"2018": 88.6, "2019": 110.8, "% Change": 25.0}}
frontend_total_2019 = df["Front-end: -- Total"]["2019"]
frontend_total_2018 = df["Front-end: -- Total"]["2018"]
answer = frontend_total_2019 - frontend_total_2018