WASHINGTON (AP) — The U.S. economy grew at a 2.9 percent rate in the July-September quarter, the strongest pace in two years, as the battered export sector rebounded and businesses finally began restocking their shelves at a faster clip. The third-quarter gross domestic product, the broadest measure of economic health, was double the 1.4 percent pace in the second quarter, the Commerce Department reported Friday. GDP growth went into a pronounced slowdown late last year.