The fall domestic film box office season now ending will equal the season’s all-time record gross of $ 833.9 million set in 1989. The challenge of reaching a $ 5 billion year lies ahead.Several strong post-Labor Day releases, combined with recent pre-holiday blockbuster openings, pushed B.O. levels more than 14% ahead of last year’s downbeat fall tally of $ 730.2 million. As forecast earlier, by Friday cumulative national box office will be virtually equal to the comparable 1991 figure of $ 4.1 billion (which included one extra week). Final 1992 U.S. box office thus depends on the upcoming six-week holiday season–and it will be a challenge because 1991 ended with an all-time record holiday season gross of $ 742.8 million. The holidays last year sported that best of all calendar configurations, a Wednesday slot for Christmas and New Year’s Day. This helped boost the year’s otherwise sluggish summer and fall. This year, the key year-end holidays fall on Friday–not the best for B.O. business, but not as bad as Saturday or Sunday, where the holidays will fall for the next two years. At this point, final 1992 B.O. is expected to exceed last year’s 52-week figure of $ 4.8 billion. But to reach the $ 5 billion record levels of 1989 and 1990, weekly grosses over the next six weeks would have to average $ 33 million higher each week over last year’s torrid levels. That’s the challenge facing the industry, but given the sensational lead-in of recent weeks, it’s not impossible.