A sharp rally in crude oil drove gains on the S&P 500 and the Dow, on Friday. But a fall in healthcare and technology stocks pushed the Nasdaq into negative territory. Oil prices jumped more than 6 percent after data showed drawdowns in U.S. stockpiles, suggesting underlying strength in the economy as demand for energy picks up.Fed Chair Janet Yellen has said, earlier, that the U.S. economy was on "a solid course," while New York Fed President William Dudley said on Friday, that a cautious and gradual approach to raising rates was appropriate.So the Dow Jones industrial average rose 35 points, or 0.2 percent, to 17,577. The S&P 500 gained 6 points, or 0.3 percent, to 2,048. And the Nasdaq Composite added 2 points, to 4,851.For the week, the Dow and S&P 500 lost 1.2 percent, each, while the Nasdaq fell 1.3 percent.The S&P 500's weekly loss was its biggest since early February.The index has mostly rallied since mid-February as oil prices rebounded and worries over China eased.US corporate earnings begin in earnest next week with reports from Alcoa and four of the big banks.