theorem Th10:
    for n holds degree (EmptyBag n) = 0
    proof
      let n;
      set b = EmptyBag n;
A1:   b*canFS(support b) = <*>NAT;
      b*canFS(support b) = <*>REAL; then
      reconsider f = b*canFS(support b) as FinSequence of REAL;
      consider f being FinSequence of NAT such that
A2:   0 = Sum f & f = b*canFS(support b) by RVSUM_1:72,A1;
      thus thesis by A2,UPROOTS:def 4;
    end;
