What was the change in U.S. property and equipment between 2018 and 2019?
{"U.S.": {"April 26, 2019": 572, "April 27, 2018": 566}, "International": {"April 26, 2019": 187, "April 27, 2018": 190}, "Total": {"April 26, 2019": 759, "April 27, 2018": 756}}
us_april_26_2019 = df["U.S."]["April 26, 2019"]
us_april_27_2018 = df["U.S."]["April 27, 2018"]
answer = us_april_26_2019 - us_april_27_2018