In the Three Tier Arch.
Presentation Part will be at the top most Level of the Data Accessing. This level usually handle user interface and give input to the Business Level and take data from the Business Level.

Business Part will be at the middle of the Three Tier Arch.. It usually hold business rules related to that application. It take input from the Presentation Level validate it and then pass it to the Data Level. It some input have invalid inputs then it pass error to the presentation level.


Data Part will be the lowest most part of the Three Tier Arch. It usually handle data saving and retriving data from the database.


So the Correct Sequence of the three tier arch. is

GUI >> Business >> Data


Cheers,

Firoz