Chapter 18 Example 2

In example 2 Andris buys an asset at the beginning of 2009 for $600 000. It has a useful life of three years and is scrapped at the end of its useful life. its profits over the next three years are:
1,800 (2009), 2,300 (2010), 2,500 (2011).

A first year tax allowance of 100% is available on this asset.
The tax rate for Andris is 25%.

Question : When calculating deferred tax for 2009, the book value is $400 000 and the tax value is 0 due to the first year 100% allowance. The deferred tax liability is therefore $100 and you release this over the next two years to write it off. But the book value in 2010 is $200 000, which gives a deferred tax liability of $50 for 2010. What happened to the deferred tax liability for 2010? i do not see where you wrote it off.

Your assistance will be deeply appreciated as I am very uncertain.