What is the ratio of contract liabilities to contract assets in 2018?
{"Contract assets, current": {"September 30, 2019": 2350, "October 1, 2018": 169}, "Contract assets, non-current": {"September 30, 2019": 581, "October 1, 2018": 507}, "Contract liabilities, current": {"September 30, 2019": 5612, "October 1, 2018": 4281}, "Contract liabilities, non-current": {"September 30, 2019": 736, "October 1, 2018": 485}}
contract_liabilities_2018 = df["Contract liabilities, current"]["October 1, 2018"] + df["Contract liabilities, non-current"]["October 1, 2018"]
contract_assets_2018 = df["Contract assets, current"]["October 1, 2018"] + df["Contract assets, non-current"]["October 1, 2018"]
answer = contract_liabilities_2018 / contract_assets_2018