What is the increase / (decrease) in the Cable-ships and submersibles from 2018 to 2019?
{"Cable-ships and submersibles": {"2019": 246.5, "2018": 251.1}, "Equipment, furniture and fixtures, and software": {"2019": 214.1, "2018": 148.0}, "Building and leasehold improvements": {"2019": 48.9, "2018": 47.3}, "Land": {"2019": 36.8, "2018": 32.8}, "Construction in progress": {"2019": 14.3, "2018": 12.9}, "Plant and transportation equipment": {"2019": 13.5, "2018": 12.0}, "": {"2019": 574.1, "2018": 504.1}, "Less: Accumulated depreciation": {"2019": 168.3, "2018": 127.8}, "Total": {"2019": 405.8, "2018": 376.3}}
cable_ships_2019 = df["Cable-ships and submersibles"]["2019"]
cable_ships_2018 = df["Cable-ships and submersibles"]["2018"]
answer = cable_ships_2019 - cable_ships_2018