Editor,In reaction to the article, Works on Nyamagabe power plant resume”, (The New Times, February 5, 2013), the Permanent Secretary  in the Ministry of Infrastructure should understand the simple rule that a lump sum contract does not necessarily equate to the final contract sum. If the contractor has suffered loss because of an error in the employers design (in this case, it could be to do with having to build another road and blast more rock out), then this would be a valid case for the contractor to claim. The amount he claims will be determined by whatever mechanism is in the contract to allow the claim. This contractor will also probably claim for delay and expense on top of the work which they claim to have done. I wish the Government and its advisors would understand the principle of lump sum in order to avoid these unnecessary complications. Rwanda cannot afford such mistakes. James, Oslo, Norway