Jack Simpson, contract negotiator for Nebula Airframe Company, is currently involved in bidding on a follow$-$up government contract. 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 $1,400$ labor hours, and the third took $1,320$ hours.

In a contract for three more units, how many labor hours should Simpson plan for?