ABC Coaches is a coach company based near London. They specialize in organizing day trips to various destinations in England. Customers of ABC Coaches include institutions such as schools, nursing homes etc. They hire coaches with drivers for trips which are organised and arranged especially for them. The manager of ABC is responsible for allocation of coaches and drivers to trips. Trip records are created when trips are arranged. If a customer (for whom a trip is being arranged) is ‘new’ then the customer’s details are recorded. Otherwise, the customer’s record is updated. Customers will typically request that a day trip be organised for them on a specific date. The number of coaches allocated to a trip depends on the number of seats required. In response to this request ABC will check to see if the required coaches can be made available on that date. If the coaches are available ABC will allocate one or more drivers and create a trip record for the customer. Customers are allowed to cancel a trip before a deposit is paid. The deposit should be paid within 7 days of the booking for the trip being taken. If a trip is cancelled after that, the deposit is kept by ABC Coaches. If a trip is cancelled the trip record will record this. ABC will request full payment for a trip in the week before it takes place. A cancelled trip is deleted from the system 6 months after cancellation. Other trip records are deleted 12 months after the corresponding trips were completed. 

 a) Using information from the case study description above produce a logical top level data flow diagram (DFD) for a booking system for the ABC Coaches system. 

b) Using information from the case study above create a use case diagram for ABC Coaches. 

c) Briefly explain the difference between a high-level DFD and a use case diagram.