The companies refused to disclose exactly what their costs would be. FCC Commissioner William Kennard and other FCC commissioners have said they wished to complete their review process by the end of the year. But in a letter sent to Steve Case's AOL Time Warner on Tuesday, the commission didn't sound as if the Dec. 31 deadline was written in stone. The FCC said it hoped to finish up the process "as soon as possible." But it did not specify any deadline date. The five-member FCC is said to be weighing whether AOL should be forced to allow its Instant Messenger service to communicate with services offered by Microsoft and Yahoo! The FCC is the last hurdle for AOL Time Warner. The Federal Trade Commission approved the mega-merger last week after the companies agreed to let rival Internet service providers onto Time Warner's cable lines. America Online shares fell $3.52, or about 7 percent, to $37.25 – matching a previous 52-week low set back in October.