Grain futures prices were mixed Friday on the Chicago Board of Trade, with the week\'s pricing largely affected by pressure from fresh South American supplies. Corn was off 5 to off 3/4, soybeans were off 3 to off 10 1/4, wheat was up 3 to up 5 and oats were up 1/2 to up 3 1/2. The prices: Corn: May 6.29 off 1, Jly 6.17 3/4 off 3/4, Sep 5.52 off 3, Dec 5.35 off 5. Soybeans: May 13.61 3/4 off 10 1/4, Jly 13.43 3/4 off 8, Aug 13.17 1/4 off 4 3/4, Sep 12.65 off 3. Wheat: May 6.99 up 5, Jly 7.04 1/4 up 4 3/4, Sep 7.12 1/4 up 4 1/4, Dec. 7.25 up 3. Oats: May 3.59 1/2 up 1/2, Jly 3.52 up 1 1/2, Sep 3.49 1/4 up 2 1/2, Dec 3.45 up 3 1/2.