The S&P 500 closed flat on Friday but ended lower for the week, with investors cautious ahead of a meeting in Europe that could decide whether Greece will default on critical loans. The Dow closed higher, boosted by strong results from component Nike Inc (NKE.N), while the Nasdaq ended solidly lower on disappointing results from Micron Technology Inc (MU.O), which weighed on chipmakers like Intel. In Europe, Greece rejected a five-month extension of bailouts on Friday, a day before euro zone finance ministers will meet to decide the country’s fate.