How to calculate the depreciation life and residual value ratio of fixed assets?

According to the Circular of the State Administration of Taxation on Clarifying the Implementation Time for Enterprises to Adjust the Proportion of Residual Value of Fixed Assets [State Taxation Letter (2005) No. 883], the residual value of fixed assets is uniformly determined as 5%.

At the same time, the new income tax law provides that there is a provision that reads: means of transportation other than airplanes, trains and ships, for four years.

So the depreciable life of a car is 4 years and the net salvage value is 5%.