After-hours buzz: Petrobras, YY, Mattress Firm & more By: CNBC.com News March 21, 2016 at 18:09 PM EDT Check out the companies making headlines after the bell Monday: Petrobras, YY, Mattress Firm and more. Read More >> Related Stocks: Adecoagro Ord Shs Tempur-Pedic International Inc William Lyon Homes YY Inc ADR