Many services, such as airlines, conduct their scheduling in two stages. First, an overall macroschedule is constructed and optimized for costs and service to the customer. This schedule is then considered to be the baseline for detailed scheduling to attempt to achieve. The second, detailed stage is then a real-time schedule to adjust the macroschedule for any necessary changes, emergencies, and so on. Describe how this might work for airlines, hospitals, schools, and urban alarm services. What serious problems might arise with this approach?