Carvana Co CVNA.N jumped 8.2% as Piper Sandler upgraded the online used-car seller's stock to "overweight" from "neutral", saying it is grossly undervalued. The three major indexes have gained for four consecutive sessions as investors took advantage of a sharp drop in stock prices since mid-August that was triggered by concerns over soaring inflation and the impact of tighter monetary policy to curb it. Policymakers last week downplayed the importance of any single data point, and emphasized their determination to keep raising rates until there is a sustained drop in inflation, which has been running at 40-year highs.