What is the difference in useful lives between buildings and that of Furniture and fixtures?
{"Land": {"Useful Lives": "Indefinite", "December 27, 2019 ": 1170, "December 28, 2018": 1170}, "Buildings": {"Useful Lives": 20, "December 27, 2019 ": 1360, "December 28, 2018": 1292}, "Machinery and equipment": {"Useful Lives": 5, "December 27, 2019 ": 21718, "December 28, 2018": 17837}, "Computers, data processing and other equipment": {"Useful Lives": 3, "December 27, 2019 ": 12686, "December 28, 2018": 11244}, "Software": {"Useful Lives": 3, "December 27, 2019 ": 29305, "December 28, 2018": 22779}, "Leasehold improvements": {"Useful Lives": 1, "December 27, 2019 ": 70903, "December 28, 2018": 60565}, "Furniture and fixtures": {"Useful Lives": 7, "December 27, 2019 ": 3309, "December 28, 2018": 3268}, "Vehicles": {"Useful Lives": 5, "December 27, 2019 ": 6410, "December 28, 2018": 2769}, "Other": {"Useful Lives": 7, "December 27, 2019 ": 95, "December 28, 2018": 95}, "Construction-in-process   ": {"Useful Lives": "", "December 27, 2019 ": 9200, "December 28, 2018": 15757}, "": {"Useful Lives": "", "December 27, 2019 ": 156156, "December 28, 2018": 136776}, "Less: accumulated depreciation and amortization   ": {"Useful Lives": "", "December 27, 2019 ": -63310, "December 28, 2018": -51500}, "Equipment, leasehold improvements and software, net": {"Useful Lives": "", "December 27, 2019 ": 92846, "December 28, 2018": 85276}}
buildings_useful_lives = df["Buildings"]["Useful Lives"]
furniture_and_fixtures_useful_lives = df["Furniture and fixtures"]["Useful Lives"]
answer = buildings_useful_lives - furniture_and_fixtures_useful_lives