theorem
   0 in dom if>0(a,k1,I,J) &  1 in dom if>0(a,k1,I,J)
proof
  set ci=card if>0(a,k1,I,J);
  ci=card I + card J +2 by Lm4;
  then 2 <= ci by NAT_1:12;
  then 1 < ci by XXREAL_0:2;
  hence thesis by AFINSQ_1:66;
end;
