Susan is trying to decide whether or not to attend college during the next 12 week session. She has the following options:

1. Attend college full time at a cost of $1,200.
2. Attend college part time at a cost of $500 and work part time earning $1,900.
3. Work full-time earning $4,500.

What is Susan's incremental profit if she chooses option 3 over option 2?