The combined entity would be valued at about $40 billion, said the people, who asked not to be identified because the discussions are private. Deliberations are ongoing and the talks could still fall apart, they said. Ackman’s special purpose acquisition company, called Pershing Square Tontine Holdings Ltd., raised $4 billion in a July initial public offering — a record-setting amount for a SPAC. Such firms go public and then find promising companies to merge with. Ackman, a hedge fund manager, has said that his firm was on the hunt for a “mature unicorn.” “We’re in a unicorn mating dance and we want to marry a very attractive unicorn on the other side that meets our characteristics,” he said in a Bloomberg Television interview at the time. “And we’ve designed ourselves to be a very attractive partner.”