A Library of Things is a community hiring service that enables people to borrow items they need occasionally instead of buying them; for example, if you need a tool for a one$-$off job in the garden or in your house you can borrow that tool $($if they have it$).$

The Library of Things has a catalogue that can be browsed by anyone, of items that can be borrowed. Anyone interested in borrowing items needs to create an account with their details $($name$,$ email, username and password, address and phone contact$).$ They can then reserve an item for a certain date, borrow an item and return an item.

a$.$Add the multiplicities to the associations in Figure $1.$

b$.$Suggest two invariants for the analysis model in Figure $1.$

c$.$How would you complete the model as given in Figure $1$ to represent the following? Indicate which class$($es$)$ are required:

The Library of Things relies on volunteers to run their services $$ librarians, repairers, delivery cyclists, and fundraisers $$ and keeps a record of their details. They may need to record different attributes for different types of volunteers.

d$.$A Repair Caf$$ helps people repair things they own and have access to experts that can support them in repairing those things for free. The Library of Things decided to also run Repair Caf$$s as follows:

a Repair Caf$$ usually runs on a Saturday afternoon supported by volunteers within different categories: clothes, electrical items, bikes. Volunteers who repair clothes provide a description of their experience; those who repair electrical goods need to have an appropriate qualification; and, those repairing bikes need to have a bike mechanic$$s qualification and an indication of which level they have reached;

a Repair Caf$$ has several slots for the specific categories that can be booked; each slot for a category has at least one expert volunteer for that category;

to attend a Repair Caf$$ you need to make a booking for a slot for a specific category.

Describe how you would extend the model in Figure $1$ to also model the Repair Caf$$s$,$ indicating which class$($es$),$ with attributes, and associations $($with multiplicities$)$ are required. You only need to draw the new bit of the diagram and indicate how it is related to the diagram of Figure $1($no need to reproduce the whole of Figure $1).$