Hi , my question is , I have some stations and each will need a worker to transport an item to another station when a request is created , after finishing the job , the worker will stay there until next request is created . I want to assign a worker which is nearest to the station to do the job , In the model I have consider each worker a token , and they will wait until they can pull a request from a list , so if more than two worker are waiting , I think I can use back order strategy to do it , but having troubles to compute the distance between the workers and stations .