An explosion Friday at a Foxconn plant in China could set Apple (NASDAQ:AAPL) back by as many as 500,000 iPad 2 units, according to a report from research firm IHS iSuppli. Foxconn is Apple's largest manufacturing partner. The exact figure depends on how long the plant is closed following the explosion, which killed three people and injured 15 others. If production is suspended for more than a month, Apple could lose more than half a million iPads, iSuppli said. However, analysts and investors brushed off concerns Monday, and said Foxconn would be able to shift production to other facilities. Article