Wall Street slides to end rough week

The S&P 500 and Nasdaq posted their largest weekly drops since March on Friday. Photo: APThe S&P 500 and Nasdaq posted their largest weekly drops since March on Friday as slowing global growth dragged commodity-related stocks lower while an earnings-fueled drop in Biogen took down the biotech sector.Biogen more than halved its revenue growth forecast for 2015 and its stock […]