What is the total unbilled receivables due between 1 to 5 years?
{"1 year or less": {"December 31, 2019": 180219, "": 60}, "1-2 years": {"December 31, 2019": 91132, "": 30}, "2-5 years": {"December 31, 2019": 30604, "": 10}, "": {"December 31, 2019": 301955, "": 100}}
total_1_2_years = df["1-2 years"]["December 31, 2019"]
total_2_5_years = df["2-5 years"]["December 31, 2019"]
answer = total_1_2_years + total_2_5_years