Please explain the both question 5 and 6 :(

Oregon Company purchased a computer that cost $12,000. It had an estimated useful life of 5 years and a residual value of $2,000. The computer was depreciated by the straight-line method and was sold at the end of the fourth year of use for a loss of $1,000. Determine the cash received from the sale. Tar Heels Company purchased a tractor on January 1, 2015, for $65,000. The tractor's useful life is estimated to be 30,000 miles and has a residual value of $5,000. If the company used the tractor 6,000 miles in 2015 and 7,000 miles in 2016, what is the book value of the tractor on December 31, 2016, using the units of output method