 This week has seen the SPAC boom shift into overdrive, with a flood of merger and initial public offering announcements. U made its debut on the New York Stock Exchange on Monday, selling 11.5 million units at 10 with each consisting of one common share and half of a warrant exercisable at 11.50 a share. Total proceeds were 115 million, which includes underwriters overallotment option of 1.5 million units. 