CHICAGO (AP) _ Grain futures were mixed Thursday on the Chicago Board of Trade. Dec. corn gained 1 cent at $5.02 a bushel. Dec. wheat gained 6.5 cents at $6.82 a bushel. Dec. oats fell by 7.75 cents at $4.11 a bushel. Nov. soybeans was off 7.75 cents at $12.83 a bushel. Beef was higher...