Answer:
a. Straight-line method.  	
Year         Depreciation expense ($) 
   1                           10,530 
   2                          14,040 
   3                          14,040 
   4                            3,510 
b. Units-of-production method.  	
Year           Depreciation expense ($) 
  1                               7,800 
  2                             14,950 
  3                             12,350 
  4                              7,020 
c. Double-declining balance method  
Year   Depreciation expense ($) 
   1                              21,735 
  2                              14,490 
  3                               4,830 
  4                               1,065 
Explanation:
(a) the straight-line method
Note: See part a of the attached excel file for the depreciation schedule for Straight-line method.
In the attached excel file, the depreciation rate used for the Straight-line method is calculated as follows:
Straight line depreciation rate = 1 / Estimated useful life = 1 / 3 = 0.3333, or 33.33%
(b) units-of-output method
Note: See part b of the attached excel file for the depreciation schedule for units-of-production method.
(c) the double-declining-balance method.
Note: See part c of the attached excel file for the depreciation schedule for double-declining-balance method.
In the attached excel file, the depreciation rate used for the Double- declining-balance method is calculated as follows:
Double-declining depreciation rate = Straight line depreciation rate * 2 = (1/3) * 2 = 0.666667, or 66.6667%
Note:
Under this double-declining-balance method, the depreciation expenses for Year 4 is calculated by deducting the residual value of $1,350 from the Year 4 Beginning depreciable amount (i.e. $2,415 - $1,350 = $1,065). The residual value of $1,350 therefore represents the book value at the end of Year 4.