What is the percentage change in income from foreign sources between 2017 and 2018?
{"Domestic": {"2019": -51396, "2018": -27494, "2017": 57493}, "Foreign": {"2019": -83450, "2018": 15951, "2017": 28742}, "(Loss) income before (benefit from) income taxes": {"2019": -134846, "2018": -11543, "2017": 86235}}
foreign_2018 = df["Foreign"]["2018"]
foreign_2017 = df["Foreign"]["2017"]
answer = ( foreign_2018 - foreign_2017 ) / foreign_2017 * 100.0