Sydney ltd used the cost model to measure its plant. plant had cost of $80000 and had a carrying amount of $70000 at 30 june 2020 and is depreciated on a straight-line basis over a 10-year period. on 31 december 2020, the directors of sydney ltd decided to change the basis of measuring the plant from the cost model to the revaluation model. plant was revalued to $70 000 with an expected useful life of 8 years.