Research and development

Amco Co carries out research and development. In the year ended 30 June 20X5 Amco Co incurred total costs in relation to project X of $750,000, spending the same amount each month up to 30 April 20X5, when the project was completed. The product produced by the project went on sale from 31 May 20X5.
The project had been confirmed as feasible on 1 January 20X5, and the product produced by the project was expected to have a useful life of five years.
What is the carrying amount of the development expenditure asset as at 30 June 20X5?

A B C D
$295,000 $725,000 $300,000

Answer is A

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The costs of $750,000 relate to ten months of the year (up to April 20X5). Therefore the costs per month were $75,000. As the project was confirmed as feasible on 1 January 20X5, the costs can be capitalised from this date. So four months of these costs can be capitalised = $75,000 × 4 = $300,000.
The asset should be amortised from when the products go on sale, so one month’s amortisation should be charged to 30 June 20X5. Amortisation is ($300,000/5) × 1/12 = $5,000. The carrying amount of the asset at 30 June 20X5 is $300,000 – $5,000 = $295,000.
If you chose C you have forgotten to amortise the development costs. If you chose B or D you have either capitalised the full amount or capitalised none of the costs.

I want to know how is it 10 months to get £75,000. How do we know this?