ANN ARBOR, MICH. — Stephen W. Sanger, retired chairman and chief executive officer of Minneapolis-based General Mills, Inc., along with his wife, Karen, have donated $20 million to the Ross School of Business at the University of Michigan to create the Sanger Leadership Center. The new center will expand the school’s leadership development programming and empower more students to become leaders who make a positive difference in the world. The Sanger Leadership Center will incorporate and expand on the current activities of the Ross Leadership Initiative — including the annual Impact Challenge and Crisis Challenge, Legacy Lab, Story Lab, skills-based workshops and a variety of learning communities — as well as the Leaders Academy, where students create, launch and lead actual businesses. The new center will be a resource for Ross students and provide them with personalized feedback, coaching and development. The center also will be a resource for Ross faculty who are developing cutting-edge ideas and new leadership practices.