How much is the change in transaction costs from 2018 to 2019?
{"": {"2019": "RMB\u2019Million", "2018": "RMB\u2019Million"}, "Transaction costs (Note (a))": {"2019": 85702, "2018": 69976}, "Employee benefits expenses (Note (b) and Note 13)": {"2019": 53123, "2018": 42153}, "Content costs (excluding amortisation of intangible assets)": {"2019": 48321, "2018": 39061}, "Amortisation of intangible assets (Note (c) and Note 20)": {"2019": 28954, "2018": 25616}, "Bandwidth and server custody fees (excluding depreciation of right-of-use assets)": {"2019": 16284, "2018": 15818}, "Depreciation of property, plant and equipment, investment properties and right-of-use assets (Note 16 and Note 18)": {"2019": 15623, "2018": 8423}, "Promotion and advertising expenses": {"2019": 16405, "2018": 19806}, "Travelling and entertainment expenses": {"2019": 1773, "2018": 1450}, "Auditors remuneration --  Audit and audit-related services": {"2019": 105, "2018": 110}, "Auditors remuneration --  Non-audit services": {"2019": 43, "2018": 26}}
transaction_costs_note_a_2019 = df["Transaction costs (Note (a))"]["2019"]
transaction_costs_note_a_2018 = df["Transaction costs (Note (a))"]["2018"]
answer = transaction_costs_note_a_2019 - transaction_costs_note_a_2018