An implementation plan should include an agreed-on time for the final rollback decision. What should this decision be scheduled? 

After the cutover to the new solution and the first set of validation tests and just before the user acceptance tests (UATs) 

after the first steps of the rollback plan have been implemented, about ten minutes before the end of the maintenance window 

just before the point of no return, which is calculated by subtracting the rollback time from the end of the maintenance window 

ten minutes before the end of the maintenance window or one hour into the implementation, whichever occur first