Electrical Cables Through Joists

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I need to run approx 12 electrical cables (Romex) perpendicular to the joists in my basement. I am planning on drilling a hole in the center of the 2X10's approx 4" from the ends of the joists. The span is 12 feet. What is the largest size hole I can make without affecting structural integrity? Is it OK for me to put all of the cables through 1 hole? If not, what is the limit? Thanks