a simple, high-level, UML class diagram

I may need help with this project:

A combined cycle gas turbine power station requires a webbased system to manage the storage and installation of spare 
parts and the acquisition of new parts from the Central Storage 
Warehouse (the CSW). The powerstation maintains an inventory 
of all the parts it owns comprising: part name, description and 
specification. There are many copies of some parts – each part 
has a unique ID, known as an asset tag number. The asset tag 
number is used when there is damage to particular parts. The 
power station also keeps a catalogue of all the possible spare 
parts types used.
Only registered maintenance engineers and team leaders are 
allowed to install and repair parts on the plant. Maintenance 
engineers and team leaders can use the parts catalogue to
search for part types and can also search the parts inventory. 
Maintenance engineers work in teams, currently: electrical, 
mechanical and environmental. Each team has its own team 
lead. However, the system needs to be flexible enough to allow 
creation of new teams in the future.
Maintenance engineers are allowed to take spare parts from the 
CSW, up to a value of £50,000. Higher value items need 
authorisation from a team leader. Spare parts are issued from 
the CSW by a Store Manager.
Occasionally a maintenance engineer needs to sign parts back 
into the CSW. Such “returns” maybe because time has run out
on the shift to install the part or because the part is no longer 
required.
Whenever a new part isinstalled in the powerstation an old part 
is removed. The old part must either be returned to the CSW for 
refurbishment or disposed of as scrap.
After store managers receive requisitions from team leaders, 
they produce purchase orders to purchase spare parts from 
suppliers. The purchase orders contain part names and 
descriptions and are sent suppliers. Suppliers then send the 
spare parts along with an invoice to the CSW. The store
managers then reconcile the invoices against the purchase 
orders to authorise payments for suppliers.
The store managers also handle spare parts returned to suppliers 
for refurbishment. When a spare part is returned to the CSW, the 
store managers produce a purchase order. Again, suppliers send 
refurbished goods (spare parts) to the CSW, where the store 
managers then reconcile invoices and authorise payments.
After the store managers authorise payments for suppliers, the 
payment transactions are actually implemented by the power 
station financial management system (FMS). A message passing 
interface is used to payment transactions. Each payment 
transaction must include: supplier name, address, phone 
number, email address, invoice number, order number, 
authorising store manager name and payment amount (in GBP).

Questions:

Draw a simple, high-level, UML class diagram of the 
system.
▪ Use the class diagram illustrate various 
relagonships between classes, such as inheritance, 
associagon and aggregagon.
▪ Show example method and ahribute names in 
classes, (think about encapsulagon, make sure 
methods go with the ahributes encapsulated by 
the class)
▪ Try to include method call and return parameters, 
where appropriate.