What is the change in the construction in progress in 2019?
{"Fiber, conduit and other outside plant(1)": {"N/A": 15, "$867": 24666, "871": 23936}, "Central office and other network electronics(2)": {"N/A": 3, "$867": 19608, "871": 18736}, "Support assets(3)": {"N/A": 3, "$867": 7984, "871": 8020}, "Construction in progress(4)": {"N/A": "N/A", "$867": 2300, "871": 1704}, "Gross property, plant and equipment": {"N/A": "", "$867": 55425, "871": 53267}, "Accumulated depreciation": {"N/A": "", "$867": -29346, "871": -26859}, "Net property, plant and equipment": {"N/A": "", "$867": 26079, "871": 26408}}
construction_in_progress_4_dollars_867 = df["Construction in progress(4)"]["$867"]
construction_in_progress_4_871 = df["Construction in progress(4)"]["871"]
answer = construction_in_progress_4_dollars_867 - construction_in_progress_4_871