Finding Common Items across all Queues

Hi Dave,

qa= {"AB","SK","OU","SK","OU"};
qb = {"EP","AB","EP","SK","EP"};
qc={23,48,45,61,99};
qd={45,21,35,23,27,83,99};

How to print common elements of two arrays(say qa and qb;qc and qd) in another queue or array