Answer:
$5,360
(not given in the options)
Step-by-step explanation:
Depreciation is the systematic allocation of cost to an asset based on estimates. It is given as 
Depreciation = (cost - salvage value)/useful life
When originally purchased, a vehicle costing $23,040 had an estimated useful life of 8 years and an estimated salvage value of $1,600
Annual depreciation = ($23,040 - $1,600)/8
= $2,680
After 4 years
Accumulated depreciation = 4 × $2,680
= $10,720
The net book value then 
= $23,040 - $10,720
= $12,320 
Since the asset's total estimated useful life was revised from 8 years to 6 years and there was no change in the estimated salvage value
New depreciation = ($12,320 - $1,600)/2
= $5,360 
The depreciation expense in year 5 equals $5,360