reserve X for ARS, a,b,c,u,v,w,x,y,z for Element of X;
reserve i,j,k for Element of ARS_01;
reserve l,m,n for Element of ARS_02;

theorem ThB1:
  for s being set holds s is Element of ARS_02 iff s = 0 or s = 1 or s = 2
  proof
    let s be set;
    the carrier of ARS_02 = {0,1,2} by Def19;
    hence thesis by ENUMSET1:def 1;
  end;
