GPA reserves the right to require all vessels using the crane (cranes) to work continuously to completion, with overtime for vessel’s account in all cases when another vessel, or vessels, is (are) awaiting berth and/or use of the crane (cranes). If a vessel should refuse to work under the above conditions, she will then lose the crane (cranes), and, if necessary, must vacate the berth. She will then take her next turn behind vessel or vessels that may be awaiting the crane (cranes) and berth, and which are willing to work overtime for earliest completion.