CHICAGO (AP) _ Grain futures were mostly lower Monday on the Chicago Board of Trade. Dec. corn fell by 6.5 cents at $5.22 a bushel. Dec. wheat was down 15.5 cents at $6.88 a bushel. Dec. oats gained 3 cents at $4.21 a bushel. Nov. soybeans was off 31.25 cents at $12.88 a bushel. Beef...