Joe started a new business this year. He had purchased a computer two years ago for $4,000 and decided to use it in his business until he could afford a new system. He could purchase a new computer with the same specifications for $1,800, but his used computer is worth only $1,100. What is his computer's basis for depreciation?
a. $1,100
b. $1,800
c. $4,000
d. The computer cannot be depreciated because it was a personal asset.