What is the sum of digital media and digital experience revenue in 2017?
{"Digital Media": {"2019": 7208.3, "2018": 5857.7, "2017": 4480.8, "% Change 2019 - 2018": 23.0}, "Digital Experience": {"2019": 2670.7, "2018": 1949.3, "2017": 1552.5, "% Change 2019 - 2018": 37.0}, "Publishing": {"2019": 115.5, "2018": 115.2, "2017": 100.6, "% Change 2019 - 2018": "*"}, "Total subscription revenue": {"2019": 9994.5, "2018": 7922.2, "2017": 6133.9, "% Change 2019 - 2018": 26.0}}
digital_media = df["Digital Media"]["2017"]
digital_experience = df["Digital Experience"]["2017"]
answer = digital_media + digital_experience