ANN ARBOR, Mich. (AP) — The University of Michigan is suing to stop a strike by graduate-student instructors after they voted to extend their walkout. The lawsuit, filed Monday, seeks an injunction that would stop the strike by the Graduate Employees’ Organization, which represents 2,000 graduate-student instructors and graduate-student assistants. The university said a strike is illegal under the contract. The strike began Sept. 8. Union members said the university isn’t doing enough to prevent the spread of COVID-19. It also wants the campus police budget cut by 50% and an end to cooperation with Ann Arbor police, among other demands.