On 5 May 2013, Lloyd Purchased a Machine for $84,000

On 5 May 2013, Lloyd purchased a machine for $84,000. The estimated life of the machine was 10 years, with an estimated residual value of $10,000. The service life in terms of "output" is estimated at 8,000 hours of operation.
-Assume Lloyd uses the units-of-output method and that the machine was in operation for 1,000 hours in 2013 and 1,800 hours in 2014. The book value of the machine at 31 December 2010 is:

A) $48,100.
B) $58,100.
C) $25,900.
D) Some other amount.