reserve X for set;

theorem Th28:
  for S being SigmaField of X ex M being Function of S,ExtREAL st
  for A being Element of S holds M.A = 0.
proof
  let S be SigmaField of X;
  consider M being Function of S,ExtREAL such that
A1: for A being Element of S holds (A = {} implies M.A = 0.) & (A <> {}
  implies M.A = 0.) by Th26;
  take M;
  thus thesis by A1;
end;
