The Tobias Company has 12 obsolete computers that are carried in inventory at a cost of $13,200. If these computers are upgraded at a cost of $7,500, they could be sold for $19,500. Alternatively, the computers could be sold "as is" for $9,000. What is the net advantage or disadvantage of re-working the computers?
A. $12,000 advantage
B. $1,200 disadvantage
C. $10,200 disadvantage
D. $3,000 advantage