The answer will be c add 1000
Presuming there is no depreciation deducted in the year of sale- the adjusted basis is $12000-$4800(depreciation for 4 years) which is $7200. The sale price is $6200 so the loss on sale is $1000 which is deducted on P&L and hence should be added back to determine cash flows from operating.
Alternatively, presuming that $1200 depreciation is claimed for the current year and last 4 years - adjusted basis is $6000 and with sale price being $6200 - gain on sale is $200. At the same time depreciation of $1200 has to be added back. Hence net amount of $1000 will have to be added.