GKN, Britain's third-largest defense company, agreed to buy Interlake Corp., a U.S. maker of ferrous powdered metals, aerospace engine components and containers, for $261 million. Under the deal, GKN would pay $7.25 for each share of Lisle, Ill.-based Interlake and also assume $292 million in debt. The British company expects the purchase to boost earnings the first year. GKN, which makes Westland helicopters, is getting out of the defense business as that industry shrinks in Europe and is concentrating more on automotive and aerospace parts. Interlake shares rose $3.44, or 96%, to close at $6.94 on the New York Stock Exchange.