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<body class='hmmessage'><div dir='ltr'>Dear eQuest users,<BR> <BR> <BR>I am obtaining the following error when I am simulating the envelope:<BR> <BR>"walls have a negative area"<BR> <BR>What's the origin of this problem? And how can I solve it?<BR> <BR>Thank you for your help,<BR>KL<BR>                                          </div></body>
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