Draw a UML Use Case Diagram, Class Diagram, and Sequence Diagram based on the following description of a Voicemail System:

The main goal of the system is to act as a messaging service for an organization-wide telephone system. The organization may have several telephone numbers and multiple calls active at a given time. The voicemail system gets activated after a callers dialed number to the telephone system goes unanswered for a given number of rings (e.g., five rings). The telephone numbers are uniquely mapped to mailbox numbers. Note that some numbers may not be assigned valid or active mailboxes (or none at all). Assume that the telephone system is responsible for functionalities such as establishing and managing the connection, managing the call (e.g., pickup, hang up), and providing information from and to the caller (e.g., the pressed phone keys, and obtain and play the actual voice message).

The voicemail system must support the callers to leave voicemails, and the mailbox owners to access and retrieve their voicemails. The owners can access and administer their mailbox with the following options: Local access: from their own (local) phone devices via a hotkey on the phone device Remote access: from other (remote) phones via dialing phone and/or extension number Web or email access: via subscription The caller can record a message verbally. The message is ended with a call hang up or a timeout in number of seconds. There is also an administration mailbox with extended functionality to manage the email system. This mailbox can access and manage other mailboxes (e.g., add or remove a mailbox and set a users password).

Tasks:

1. Draw the use case diagram

2. Describe three different scenarios that can occur (from the use case diagram).

3. Draw the UML sequence diagrams for these three scenarios

4. Draw the UML class diagram.