Groupe Bull SA and Zenith Electronics Corp are now almost $100m apart on the right price for Bull to pay for Zenith Data Systems: Zenith reckons Bull owes it another $49.m but Bull opines that Zenith should pay back about $49m of the $496.4m already handed over; if the two companies are unable to settle their differences within the next 30 days, the issue will go to an accounting firm for arbitration.