Stocks quickly reversed higher after a weak open Monday to finish with respectable gains. The Dow Jones industrial average and S&P 500 added 0.7% each, while the Nasdaq rose 0.6%. Small-caps underperformed, with the Russell 2000 gaining 0.4%. Preliminary numbers show volume rose across the board from Thursday’s preholiday session. Stocks opened lower following Friday’s disappointing jobs report. U.S.