Non-Current Asset Depreciation

I am not sure I fully understand revalued depreciation.

Q: On 1 January 20X7 a building with a carrying amount of $700,000 was revalued to $750,000. The remaining useful life at that date was 25 years.

On 1 January 20X7 the building was sold for $800,000.

What profit on disposal of the building will be reported in the statement of profit or loss for the year ended 31 December 20X7?

A. $110,000
B. $50,000
C. $160,000
D. $156,000

In my opinion B would be the answer as depreciation would not have taken effect at the time it was sold. The date which it was revalued is the date it was sold, at the beginning of the month. If it was at the end of the month then a month’s deprecation would be charged.

The answer in the book is A.

Am I missing something? I am now confused.

The question didn’t state that depreciation is applicable in the year of disposal

Please help.