Fair Value at Acq

I have an issue working out the FV adjustment relating to bang of the crash bang wallop question in the Kaplan P2 book.
All ‘$000
FV = 120
One year on asset unadjusted for FV is worth 80
UEL of assets is 5 years (doesn’t say from when)

Assuming s/l depn this does not appear to compute as the answer upon checking advises the FVA to be 15, which means the original value of the assets must have been 105 assuming they mean 5 years from doa then the book value was more likely 100 and the FVA 20?

Anyone let me know where I am being completely dumb?

Many thanks