c$)$ The following represents part of the facts gathered during an interview about a Sales System:

A customer may send zero, one or many Requests for Quotation $($RFQ$).$ An RFQ is sent by a particular customer.

An RFQ may contain one or many items. An item may be contained in one or many RFQ$.$ A customer may send one or many sales orders. A sales order is sent by only one customer.

Using the standard notation, draw an entity$-$relationship diagram $($ERD$)$ for the above scenario. You are NOT required to resolve any many$-$to$-$many relationships between the entities.

$(7$ marks$)$

d$)$ Without referencing to the scenario in c$)$ above, and by using the Database Design Language $($DBDL$)$ format, identify the relevant data attributes for CUSTOMER and SALES ORDER entities. Show clearly both the primary and foreign keys. Example of a DBDL format: PAYMENT $($Payment No$.,$ Date, Amount, Invoice No$.*).$

$(6$ marks$)$

$[$Total: $25$ marks$]$