ack 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 $2,500$ labor hours, the second took $2,125$ labor hours, and the third took $2,000$ hours.

How many labor hours should Simpson plan for the $5$th unit? $($Round your answer to the nearest whole number.$)$