Table Based Depreciation Methods

Hello,

I am trying to setup a table based depreciation method which should achieve the following example.

Useful Life: 3 Years

Method Type: Table/Calculation Basis: NBV

Year 1: 50%

Year 2: 25%

Year 3: 25%

Here's my problem. As per Oracle, I have to define, 4 years in the table. So I was planning on defining the foillowing:

Year 1     Period 1     0.50

Year 2    Period 1     0.25

Year 3     Period 1    0.25 and so on. But Oracle requires that I define Year 4 as well..so how could I define the rate in the above example? How do I achieve this mathematically?

Thanks in advance!!

P.S. We are on 11.5.10