SpaceX underwriters have officially exercised their overallotment of shares in the historic initial public offering, bringing the total raised to $85.7 billion, according to an investor relations update out Monday.Elon Musk's space and artificial intelligence company raised an initial $75 billion on Thursday, making it the biggest IPO ever.SpaceX's brokers, which include Goldman Sachs and Morgan Stanley, had the option to buy an additional 83.3 million shares as part of the overallotment, which ...