What is the average total fees for 2018 and 2019?
{"": {"2019": "\u20acm", "2018": "\u20acm", "2017": "\u20acm"}, "Parent company": {"2019": 2, "2018": 2, "2017": 2}, "Subsidiaries": {"2019": 14, "2018": 14, "2017": 13}, "Subsidiaries  new accounting standards1": {"2019": 1, "2018": 5, "2017": 1}, "Audit fees:": {"2019": 17, "2018": 21, "2017": 16}, "Audit-related fees2": {"2019": 2, "2018": 5, "2017": 4}, "Non-audit fees:": {"2019": 2, "2018": 5, "2017": 4}, "Total fees": {"2019": 19, "2018": 26, "2017": 20}}
total_fees_2019 = df["Total fees"]["2019"]
total_fees_2018 = df["Total fees"]["2018"]
parent_company_2019 = df["Parent company"]["2019"]
answer = (total_fees_2019 + total_fees_2018) / parent_company_2019