EXHIBIT 8.1 {Letterhead of Preston Gates & Ellis LLP} September __, 2004 Primus Knowledge Solutions, Inc. 1601 Fifth Avenue, Suite 1900 Seattle, WA 98101 RE: MERGER PURSUANT TO THE AGREEMENT AND PLAN OF MERGER (THE "AGREEMENT") DATED AS OF AUGUST 10,...Merger Agreement • September 8th, 2004 • Art Technology Group Inc • Services-prepackaged software
