please calculate the fair value

Construction of the building commenced in June 2014 and was completed and available hor use on 1 January 2016 at a cost of N$3 000 000. Its total estimated useful life is 20 years. Fair values are now considered reliably measurable and the accountant is adamant that the asset should either be measured under the fair value model forthwith or that the depreciation on the building should be measured using an estimated residual value of N$500 000 (previously the residual value was nil). The estimated useful life has remained unchanged. The fair value on 31 December 2019 was N$6 000 000