Please show complete work and list the equations used if possible.

please solve without excel

An oil drilling rig can be obtained for $150.000. At the end of 6 years, it can be sold for $20,000. Compute the depreciation schedule for the drilling rig through year 4 using the following methods. (a) Sum-of-years' digits depreciation (6) Double declining balance depreciation (c) MACRS depreciation