The RiverHill County Public Library has 516 employees, including 163 librarians. A study reveals that seven out of ten supervisors in the library branches are male, although men make up only 25 percent of the branch librarians. In order to increase the number of female librarians at the supervisory level, the library decides to implement an affirmative action plan that would consider gender as one component of the decision when promoting librarians until a point when the imbalance is corrected. Is this affirmative action plan valid? Explain what it would need to include to be valid.