reserve W,X,Y,Z for set,
  f,g for Function,
  a,x,y,z for set;
reserve u,v for Element of Tarski-Class(X),
  A,B,C for Ordinal,
  L for Sequence;

theorem Th24:
  Y in Tarski-Class X implies card Y in card Tarski-Class X
proof
  assume
A1: Y in Tarski-Class X;
 bool Y c= Tarski-Class X
  by A1,Th3;
  then  card
 Y in card bool Y & card bool Y c= card Tarski-Class X by CARD_1:11,14;
  hence thesis;
end;
