What is the difference between the R&D expensed in 2019 and 2018?
{"R&D expensed": {"2019": 1355, "2018": 1883}, "Capitalized software development costs": {"2019": 1074, "2018": 1276}, "Total resources expensed for R&D": {"2019": 2430, "2018": 3159}}
rd_expensed_2019 = df["R&D expensed"]["2019"]
rd_expensed_2018 = df["R&D expensed"]["2018"]
answer = rd_expensed_2019 - rd_expensed_2018