reserve a,b,c for set;

theorem Th24:
  for X,x0 being set for A being Subset of DiscrWithInfin(X,x0) st
  A is finite holds Cl A = A
proof
  let X,x0 be set;
  let A be Subset of DiscrWithInfin(X,x0);
  assume A is finite;
  then A is closed by Th20;
  hence thesis by PRE_TOPC:22;
end;
