Bert, Roger and Don have formed a general partnership. Don has contributed $1,000 and does much of the work and planning. Roger has contributed $2,000 but does not do much of anything. Bert has promised to contribute $3,000, but has not done so, telling the others he should not have to pay since he is so valuable to the business. Don has entered into a contract that proves to be a bad deal for the partnership and results in a loss of $6,000. What is the maximum potential liability of Roger for this loss?