straight-line method depreciation

(Question 34.6 F3 Bpp revision kit) A business purchased an asset on 1 January 20X1 at a cost of 160,000. The asset had an expected life of 8 years, and the residual value of $40,000. The straight line method is used to measure depreciation. the financial year ends on 31 December.

At 31 December 20X3, the estimated remaining life of the asset from that date is now expected to be only three more years, but the residual value is unchanged.

What will be the net book value of the asset as at 31 December 20X3, for inclusion in the statement of financial position?

A $97,500
B $100,000
C $107,500
D $115,000

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Sir, the answer given in the book back is ‘C’ but I couldn’t figure out how it has come?