(a) Suppose you are working on the use case diagram of a system that has to serve a call centre. You have a use case "Take call" that models the handling of a customer call, from start to end. Within every call, the Operator (which is actor of the use case "Take call") needs to run another use case "Retrieve customer details" (with obvious meaning). You want to reuse the latter use case from another use case diagram. Draw a (fragment of use case diagram with the two above use cases and suitable constructs for reuse. (10 marks) (b) Consider a subsystem as in the figure below, with two classes C1 and C2, with static (class-scope) operations 1 () and 2 (int) respectively. The subsystem needs to export an operation g() that is specified in pseudo-code as follows: C1.fl(); for j-1 to 10 C2.2 (j); Apply the Faade pattern to make the operation g() public to clients of the subsystem, adding suitable classes as necessary. Give the implementation in pseudo-code of all operations you add. Assume no other operations are to be made public to the subsystem's clients. Use a diagram if you prefer a graphical representation. (10 marks) CI C2 110 2 (int) Subsystem