What is the average aggregate size of the facilities in Arizona and Washington?
{"California": {"Number of Facilities": 10, "Aggregate Size": 618900}, "New York": {"Number of Facilities": 1, "Aggregate Size": 231100}, "Texas": {"Number of Facilities": 3, "Aggregate Size": 214300}, "Illinois": {"Number of Facilities": 3, "Aggregate Size": 144200}, "Ohio": {"Number of Facilities": 2, "Aggregate Size": 120400}, "Maryland": {"Number of Facilities": 3, "Aggregate Size": 115300}, "Nevada": {"Number of Facilities": 1, "Aggregate Size": 74000}, "Oregon": {"Number of Facilities": 1, "Aggregate Size": 55500}, "Ontario": {"Number of Facilities": 1, "Aggregate Size": 51300}, "Florida": {"Number of Facilities": 2, "Aggregate Size": 48300}, "New Jersey": {"Number of Facilities": 1, "Aggregate Size": 38400}, "Connecticut(2)": {"Number of Facilities": 1, "Aggregate Size": 29200}, "British Columbia": {"Number of Facilities": 1, "Aggregate Size": 24900}, "Alberta": {"Number of Facilities": 2, "Aggregate Size": 16500}, "Arizona": {"Number of Facilities": 1, "Aggregate Size": 14500}, "Washington": {"Number of Facilities": 1, "Aggregate Size": 10500}, "Total": {"Number of Facilities": 34, "Aggregate Size": 1807300}}
arizona_aggregate = df["Arizona"]["Aggregate Size"]
washington_aggregate = df["Washington"]["Aggregate Size"]
answer = (arizona_aggregate + washington_aggregate) / 2.0