Behind strong returns for shares of UnitedHealth and Dow Inc., the Dow Jones Industrial Average is trading up Friday morning. The Dow (DJIA) was most recently trading 71 points, or 0.3%, higher, as shares of UnitedHealth (UNH) and Dow Inc. (DOW) are contributing to the blue-chip gauge’s intraday rally. UnitedHealth’s shares are up $6.41, or 2.8%, while those of Dow Inc. are up $0.54, or 1.2%, combining for a roughly 47-point boost for the Dow.