develop a simple calculator. The calculator has two sets of keys: ten numeric keys (0-9) and five operator keys ("+","-","*", "="). The keys are displayed on the calculator interface. Users can select the numbers and the operators with mouse. The selections as well as the results are displayed on a display area of the interface. In order to perform any calculation, the user has to make selections in the sequence: NUM1→operator→ NUM2→"=". For example, to add the numbers 2 and 32, the user has to select 2→+→32→=.

Answer the following.
a) Show any TWO use cases [answer with diagram, mainline sequence and alternate sequence (if any)]?
b) Identify the classes for object-oriented design of the calculator system (with ONLY one line description of each class).
c) Show the class diagram (ONLY the diagram, NO need to provide all the class definitions).