What was the change in work in process between 2018 and 2019?
{"Raw materials": {"August 31,2019": 2310081, "August 31,2018": 2070569}, "Work in process": {"August 31,2019": 468217, "August 31,2018": 788742}, "Finished goods": {"August 31,2019": 314258, "August 31,2018": 659335}, "Reserve for excess and obsolete inventory": {"August 31,2019": -69553, "August 31,2018": -60940}, "Inventories, net": {"August 31,2019": 3023003, "August 31,2018": 3457706}}
work_in_process_august_31_2019 = df["Work in process"]["August 31,2019"]
work_in_process_august_31_2018 = df["Work in process"]["August 31,2018"]
answer = work_in_process_august_31_2019 - work_in_process_august_31_2018