Two individuals each receive an envelope filled with cash. The number of dollars is greater than or equal to $0 and less than or equal $1,000 with all possibilities in between equally likely. After each person looks at their envelope (and counts the money) they have the option of keeping the envelope or exchanging the envelope with the other person. If both people choose to exchange the envelope, the envelopes are exchanged. If either person chooses to keep her envelope, then no exchange takes place. What is the maximum amount of money a person will choose to exchange in an equilibrium?