Jack Simpson, contract negotiator for Nebula Airframe Company, is currently involved in bidding on a follow-up government contact. In gathering cost data from the first three units, which Nebula produced under a research and development contract, he found that the first unit took 2,000 labor hours, the second took 1,800 labor hours, and the third took 1692 hours. In a contract for 3 more units, how many labor hours should Simpson Plan for?