What was the change in the amount Thereof committee remuneration in 2019 from 2018?
{"Total compensation": {"2019": 3770, "2018": 3702, "2017": 3663}, "Thereof fixed compensation": {"2019": 3218, "2018": 3162, "2017": 3135}, "Thereof committee remuneration": {"2019": 553, "2018": 540, "2017": 528}}
thereof_committee_remuneration_2019 = df["Thereof committee remuneration"]["2019"]
thereof_committee_remuneration_2018 = df["Thereof committee remuneration"]["2018"]
answer = thereof_committee_remuneration_2019 - thereof_committee_remuneration_2018