A building maintenance bought a pump set for 90,000. Installation cost amounted to P10,000. The pump set is to have a salvage value of P5,000 at the end of its 17 years life. Determine the depreciation charge during the 13th year and the book value at the end of 13 years by the (a) declining balance method, (b) double declining balance method, (c) sinking fund method at 12% and (d) Sum of the years digits method