1. An online computer assembling mobile phone Application provides interfaces for end users to assemble computers by selecting computer accessories with different configurations from different factories themselves. For example, users can select main-case, main-board, CPU, memories, power and screen from different factories. Users need to open the App first, register an Account in the App by inputting usemames and passwords. Then they could select different components under guidance of the APP. A computer usually consists of a main-case, a main-board, one to multiple CPUs, one to multiple memory card, zero to multiple display card, one to multiple mechanical hard disks or SSD disks, one power, zero to multiple screens, one mouse and one keyboard. Components have some common attributes of name, model type, manufacturer, date of produced. CPU has the unique attributes of frequency, core numbers, etc. Memory has the unique attributes of memory size, rank number, etc. Similarly, other components have some other unique attributes. There are mainly two types of screens: one is curved screen and another type is flat screen. There are two types of CPU, one is for business (such as Xeon) and another is for home and usual use (Core i5, Core i7). (1) Prepare a domain class diagram for this software including classes "Computer, Component, Maincase, Mainboard, CPU, Business-CPU, Home-CPU, Memory-card, Power, Screen, User, Account, etc" (15') (2) Add appropriate properties to classes in the domain class diagram (10') (3) Build an activity diagram to describe the process of registering and logging into the system. Tips for the process: The user needs to input a user name first. Then the system will check with remote server whether the user name is available. If it is, the password need to be input two times. If the password is not input correctly or too simple, a message is displayed to notice user to change it. If all of these information is correctly provided, the account is created for the user. Next, the user need to go to the login page to login by inputting username and password. (10')