CHICAGO (AP) _ Grain futures were mixed in early trading Friday on the Chicago Board of Trade. Dec. corn was unchanged at $4.51 a bushel. Dec. wheat was up 1.25 cents at $6.05 a bushel. Dec. oats was unchanged at $3.43 a bushel. Nov. soybeans rose by 0.75 cent at $12.21 a bushel. Beef was...