The economy continued to grow in February but slowed from the sharply increased growth rate registered in January, according to the National Assn. of Purchasing Managers. The association's composite index declined to 51.9% last month from 55.8% in January. The growth rate in new orders and production has also slowed since January, but that "should not be significant enough to dampen prospects for a respectable first quarter," said Robert J. Bretz, chairman of the association's survey committee. Vendor deliveries improved slightly, but members reported steel supplies were tight as USX, formerly U.S. Steel, gradually resumed production. An equal number of members reported inventories higher and lower.