A company purchases a machine for $96,000 on January 1, 2013. Its useful life is five years or 100,000 units of product, and its salvage value is $8,000. During 2013, 10,000 units of product are produced. Compute the book value of this machine on December 31, 2013, assuming

(a) straight-line depreciation and

(b) units-of-production depreciation.