In 2019, Firm X had revenue of $200 million, costs excluding depreciation of $70 million, depreciation expense of $20 million, interest expense of $40 million and capital expenditure of $15 million. Net working capital was $35 million at the end of 2018 and $25 million at the end of 2019. The corporate tax rate is 20%. 

What was the firm's unlevered cash flow in 2019?