Walgreen Profit Rises 30.5 Percent  CHICAGO (Reuters) - Walgreen Co. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=WAG.N target=/stocks/quickinfo/fullquote"&gt;WAG.N&lt;/A&gt;, one of the  largest U.S. drugstore chain operators, on Monday posted a 30.5  percent jump in quarterly profit, its largest increase in four  years, boosted by higher sales of prescription drugs and  general merchandise.