Capital Taxes

Please can you help me with the Tax depreciation ? For the year ended 30 September 20X2, KJ’s statement of profit or loss included a profit before tax of $247,000. KJ’s expenses included political donations of $19,000 and entertaining expenses of $11,000. KJ’s statement of financial position at 30 September 20X2 included plant and machinery with a carrying value of $168,500. This is comprised of plant purchased on 1 October 20X0 at a cost of $280,000 and machinery purchased on 1 October 20X1 at a cost of $150,000. KJ depreciates all plant and machinery on the straight line basis at 10% per year. All expenses other than depreciation, amortisation, entertaining, taxes paid to other public bodies and donations to political parties are tax deductible. Tax depreciation is deductible as follows: 50% of additions to property, plant and equipment in the accounting period in which they are recorded 25% per year of the written-down value (i.e. cost minus previous allowances) in subsequent accounting periods except that in which the asset is disposed of. The corporate tax on profits is at a rate of 25%. Calculate the tax payable by KJ for the year to 30 September 20X2. (Your answer should be rounded down to the nearest $.) Tax depreciation: $ First year allowance 150,000 × 50% = 75,000 Annual allowance (280,000 – 140,000 FYA 50% for 30/9/X1) × 25% = 35,000 _______ Total tax depreciation 110,000 I don't understand how the Annual allowance is calculated ? I thought normally you take first year allowance and work out 25% of that ?