Today, I had two of the team members come in to say that they wanted to apologize and that they didn't realize what the team member that wrote up the answer was doing.  They said he was writing the answer down while they were talking and it was pretty close to what they had been talking about and none of them recognized that it was from the textbook, so they all just signed the page.  I do actually believe them (though perhaps they should have read his answer more closely), mostly because it was very hard for me to believe that an entire team would endorse copying the answer from the textbook.  They asked what they could do and I wasn't sure how to respond (generally, I do not allow students to resubmit plagiarized work for a grade).  I suggested they talk to their entire team and propose a solution as a team.  I then said I would consider their proposal, without making any promises.  Any suggestions on how to handle this kind of situation?