Need some help for a college class.

Designing a system for a company much like Fed-Ex for Shipment tracking.
Information demands listed are package tracking, customer/contract information and AirBill/package information.

Functional Areas
Call center, Accounts Receivable, billing, sales, field service, Corporate service and automated service.

My question is when i design the Context diagram and lower level diagrams which one am i supposed to use the information demands or functional or something totally different?

I'm waiting for an email back from my instructor, but i hate waiting so i posted here.