Jakub Porzycki | Nurphoto | Getty ImagesOpenAI has hired Mike Liberatore, former finance chief at Elon Musk's xAI, to be the artificial intelligence startup's business finance officer, responsible for overseeing its massive infrastructure spending. Liberatore, who left xAI in July after just three months on the job, begins Tuesday, a company spokesperson told CNBC. He will report to CFO Sarah Friar and work with Greg Brockman's team, which manages the contracts and capital behind OpenAI's comput...