Consider the following extract of an E-R diagram for Demi's Goods (DG) Pty Ltd and answer the following questions

a) For a specific item of inventory (i.e. same Item ID number). Are all purchases made at the same price? Explain why / why not with relation to the diagram. (2 marks)

b) For each of the "Line" entities (e.g. sales order line) there are two Primary Keys, explain why. (2 marks)

c)

consists of triggers Goods Movement Goods Receipt PK GR ID Date Item ID Date triggered by Item ID Received by Quantity Goods Receipt PO ID Purchase Qty Purchase Price Purchase Total Shipping ID PK Item ID Sales Price ID Description Sale Total FK Sales Price ID Quantity _ tracked by . Cost Prlce 4 Cost Prrce Quantity on Value hand Quantity triggered by Reserved Reorder Point On order requested by appears on picks triggers requests /+\\ A , Pickling Line Shipping Line Sales Order LIne PK Pickin ID PK Shi in ID PK Sales ID 9 pp 9 PK Item ID Item ID uantit Quantity Q y part of part of part of consists of consists of consists of triggers triggers Picking Slip Sales Order _ 4 Shipping Document trlggered by PK Sales ID PK Picking ID PK Shipping ID Customer ID FK Sales ID ? Order Date Date Picking ID Shipping Date Status (not Shipping Date icked, artiali . Sicked p ty FK Shipped by completed) FK Picked by triggered by placed by places Customer PK Customer ID Address Name