
theorem
  for G being nonnegative-weighted WGraph, W being Walk of G holds 0 <=
  W.cost()
proof
  let G be nonnegative-weighted WGraph, W be Walk of G;
  for i being Nat st i in dom W.weightSeq() holds 0 <= (W.weightSeq()).i
  by Th28;
  hence thesis by RVSUM_1:84;
end;
