 reserve o,o1,o2 for object;
 reserve n for Ordinal;
 reserve R,L for non degenerated comRing;
 reserve b for bag of 1;

theorem Th30:
   for R holds (BSFSeri(R)).(1.Formal-Series(1,R)) = 1.(Formal-Series R)
   proof
     let R;
     consider e1 being Series of 1,R such that
A1:  e1 = (1.Formal-Series(1,R)) &
     (BSFSeri(R)).(1.Formal-Series(1,R)) = e1*(NBag1) by Def4;
     e1 = 1_(1,R) by A1,Def3; then
     (BSFSeri(R)).(1.Formal-Series(1,R))
     = (0_(1,R)+*(EmptyBag 1,1.R))*(NBag1) by A1 .= 1_.(R) by Th23
     .= 1.(Formal-Series R) by POLYALG1:def 2;
     hence thesis;
   end;
