Tax allowable depreciation Straight line method

I cannot believe this would ever be the case in the exam (and in the exam TAD is almost always reducing balance). If it was the case then the TAD would be 25% of cost for each of the first four years. In the 5th and final year there would be the balancing charge of the difference between the sale proceeds and the tax written down value (the tax written down value would obviously be zero) in the normal way. If there were no sale proceeds then there would be no allowance or charge in the final year.