Want to confirm timing of tax savings and cost of capital (before or after tax?)

A company has 31 December as its accounting year end. On 1 January 20X5, a new machine costing $2,000,000 is purchased. The company expects to sell the machine on 31 December 20X6 for $350,000.

The rate of corporation tax for the company is 30% and tax is paid at the end of the year in which it is incurred. Tax-allowable depreciation is obtained at 25% on the reducing balance basis, and a balancing allowance is available on disposal of the asset. The company makes sufficient profits to obtain relief for tax-allowable depreciation as soon as they arise.

If the company’s cost of capital is 15% per annum, what is the present value of the tax savings from the tax allowable depreciation at 1 January, 20×5 (to the nearest thousand dollars)?

I just wanted to confirm two things in this question. Since machine was purchased on 1 Jan 20×5, should i take this cashflow to be shown in year 0 as it happened at the start of year 1? (not really required for this question, I am only asking for my own understanding).

If I show it to be in year 0, then only I can discount the tax saving at 31 dec 20×5 using year 1’s discount factor (because no discounting in year 0). Can you let me know if my concept is correct?

And also, I am a bit confused shouldn’t we use the post tax cost of capital for discounting?? I don’t understand when do we use it and when do we not use it?

Please let me know. Thanks in advance!