Answer and Explanation:
The Journal entry is shown below:-
On July 1 2016
Computer Dr, $2,100 ($1900 + $150 + $50)
To Cash $2100
(Being purchase of computer is recorded)
On Nov. 3 2016
Repairs and maintenance Dr, $140
To Cash $140
(Being ordinary repairs is recorded)
On Dec 31 2016
Depreciation expense Dr, $ 400 ($2100 - $500 ÷ 4)
To Accumulated depreciation $400
(Being depreciation expense is recorded)
On Dec 31 2017
Depreciation expense $400
To Accumulated depreciation $400
(Being depreciation expense is recorded)
On Jan 1 2018
Computer Dr, $300
To Cash $300
(Being upgrade cost is recorded)