Stocks finished narrowly mixed Monday in what is traditionally the start of the year’s dullest trading week. Volume rose from Friday’s pace. The Nasdaq rose a fraction; the S&P 500 rose 0.1%; the Dow Jones industrial average fell 0.1%. In the stock market today among IBD 50 stocks, 27 were higher and 23 were lower. The best performer was Avis Budget Group (CAR), up nearly 3%.