Depreciation questions

(i) The Machinery account in the records of a company for the year ended 31 December 2018 is shown below:

Machinery – at cost
£ £
Opening bal. 300,000 30 November Disposals 120,000
1 June Bank 72,000 Bal c/d 252,000
372,000 372,000

The company’s policy is to charge straight line depreciation at 10% per year on a proportionate basis.

300,000 – 120,000 = 180,000
180,000 + 72,000 = 252, 000

What should be the charge for depreciation in the statement of profit or loss for the year ended 31 December 2018?

A £25,200

B £20,400

C £33,200

D £30,000

Hi can you please explain this question to me step by step and how to get the answer. I’m quite confused
Thank you!