How to report cost basis or realized gain(loss) from Baxalta merger when origional stock purchashed was Baxter

Hi I received a 1099-B with a transaction dated 6/3/16 for Baxalta (merger) saying I sold 1,152 shares with proceeds of $52,042. The cost basis and gain are not listed as the original purchased stock was Baxter from Dec 1, 2001. Can you please help me with how I should be reporting the cost basis and gains? Thanks!