Thurber company purchased equipment for 710,000 which was estimated to have a useful life of 10 years with a salvage value of 10,000 at the end of that time. Depreciation has been entered for 7 years on a straight line basis. In 2013, it is determined that the total estimated life should be 15 years with a salvage value of 4,000 at the end of that time. instructions: (a) prepare the entry (if any) to correct the prior years' depreciation. (b) prepare the entry to record depreciation for 2013