reserve A,X,X1,X2,Y,Y1,Y2 for set, a,b,c,d,x,y,z for object;
reserve P,P1,P2,Q,R,S for Relation;

theorem
  P c= R & X c= Y implies P"X c= R"Y
proof
  assume P c= R & X c= Y;
  then P"X c= R"X & R"X c= R"Y by Th133,Th134;
  hence thesis;
end;
