Sprint Corp. FON Group shares, big losers in last year's up-and-down market, rallied sharply after the Federal Reserve Board's surprise cut in short-term interest rates last week. FON Group is the publicly traded unit of Sprint Corp. that includes wireline telecommunications services (it's the No. 3 U.S. long distance provider). Investors also bid up shares in Sprint rivals AT&T Corp. and WorldCom. In trading Friday, Sprint closed at $26, up 28% for the week.