Mark is managing by using a delegative or laissez-faire management style. This style of management involves delegating tasks and responsibilities to employees, and giving them the freedom to make decisions and carry out their work on their own. The manager's role is to provide guidance and support, but not to micromanage or closely supervise employees. This style of management is often used when employees are highly skilled and experienced, and can be trusted to work independently. In this case, Mark has extensively trained his staff, and trusts them to carry out their responsibilities without close supervision. However, when unexpected events occur, Mark steps in to take action and provide guidance as needed. This approach can be effective in empowering employees and promoting a sense of ownership and responsibility, while still allowing the manager to maintain control and respond to unforeseen situations.