题目

 (西安交大附中2007—2008学年度下学期高三第四次模拟考试D篇) Ralph Ellison’s novel, “Invisible（看不见的） Man”, was published in nineteen fifty-two. Ellison was at once called a major new writer. The book won the National Book Award ,a high and rare honor for a first novel.        Since then millions of copies have been printed .The book is still used in many universities and other schools. One professor said that he has used the book in his teaching for twenty-five years. He said that each time he returns to “Invisible Man” he finds new idea已知点A（4,0）、B（4，4）、C（2，6），求AC与OB的交点P的坐标.