U.S. stocks were mostly higher in midday trading Friday as negotiators continued to work toward a solution to Greece's debt problems, AP reported. The Dow Jones industrial average rose 78 points, or 0.4 percent, to 17,968 as of 12:15 p.m. Eastern. The Dow was largely lifted by shares of Nike, which rose after posting strong quarterly results. The Standard & Poor's 500 index rose two points, or 0.1 percent, to 2,104 and the Nasdaq composite fell 21 points, or 0.4 percent, to 5,090. Nike rose $4.44, or 4 percent, to $109.66 after the athletic shoe and apparel maker posted quarterly results that beat analysts' expectations. On Friday, Chinese stocks plunged more than 7 percent. The Shanghai composite closed at 4,391.91. It reached 5,300 just two weeks ago. Benchmark U.S. crude oil fell 26 cents to $59.43 a barrel on the New York Mercantile Exchange. Brent crude, a benchmark for international oils used by many U.S. refineries, was little changed at $63.19 a barrel in London. In currency trading, the euro fell to $1.1147 while the dollar rose to 123.94 Japanese yen.