Thurber Co. 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.