Production activity rose slightly in February, Dunn and Bradstreet said Sunday, as its purchasing manager's index rose 0.8% for the month. The monthly rise was the was the fourth in a row. The index came in at 57.8% - values above 50% indicate economic expansion. The rise was attributed primarily to a sharp increase in demand for exports, which rose for the 12th straight month, to 60.5%. February inventories of raw and finished products also rose, but were somewhat offset in the index by a dip in the local demand component of the index, which in turn brought down production and unemployment.