What is the total stock-based compensation expense related to research, development, and other related costs from 2017 to 2019?
{"Research, development and other related costs": {"2019": 14643, "2018": 13168, "2017": 13277}, "Selling, general and administrative": {"2019": 16911, "2018": 17843, "2017": 20185}, "Total stock-based compensation expense": {"2019": 31554, "2018": 31011, "2017": 33462}}
total_2019 = df["Research, development and other related costs"]["2019"]
total_2018 = df["Research, development and other related costs"]["2018"]
total_2017 = df["Research, development and other related costs"]["2017"]
answer = total_2019 + total_2018 + total_2017