The stock market was rocked by big swings throughout last week amid inflation fears, but despite the volatility, the two key indexes ended the week essentially flat, thanks largely to a strong rally on Thursday. Strong results for tech stocks including Intel, Yahoo! and Google were countered by bad news from Costco and Maytag, which had investors fearing a drop in consumer spending. And again, oil prices were up. For the week, the Dow Jones industrial average closed at 10,157.71, up less than a point, while Nasdaq trading was completed at 1932.19, up just more than a point. All of the major ad-agency holding-company stocks traded up, if only slightly, for the week. WPP, which reported double-digit revenue growth for the first quarter, closed at $57.15, up 2.5 percent. The other two players were essentially flat, with Omnicom finishing its week at $83.99 and IPG ending at $13.07.