BPP revision kit 32

Q: Carter Co vacated an office building and let it out to a third party on 30 June 20×8. The building had an original cost of $900,000 on 1 Janauary 20×0 and was being depreciated over 50 years. It was judged to have a fair value on 30 June 20×8 of $950,000. At the year-end date of 31 Decemeber 208 the fair value of the building was estimated at $1.2 million.

Carter Co uses the fair value model for investment property.
What amound will be shown in revaluation surplus at 31 Decemebr 20×8 in respect of building?

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Hi,

I am not sure why the increase between 30.6.×8 and 31.12.×8 will be credited to profit or loss when the increase between 01.01.×8 will be shown in the revaluation surplus.