pku, tsinghua or fudan is necessary, 5% rank in the department is also necessary, these together are not sufficient, luck is important, for undergraduate applicant, your school brand is the most important, then if your school passes the screening rule, then your gpa or rank.
GPA I think is not a big problem in this case. Unlike a postgraduate, 3.5+ is good for an undergraduate student.If possible, work for 1 yr for a fortune 500 company as like management trainee or sth. It would be much better for you to apply business school if you get nice working experience.