Selling a book that one got for free

Am I allowed to sell a book I got for free?

I ordered a secondhand book online for a class I'm taking. It arrived very quick, and it looked completely new, not secondhand at all, but I no longer needed it as I had already bought the ebook. I put the book for sale online. What I usually do is sell it for 2x or 3x the price I paid, but still cheaper than the retail price. But then, a few days later, I got another copy of the book in the mail, and this one looked more like a secondhand book with highlights and stuff. I thought maybe the company made a mistake and sent me 2 copies, but I just remembered, about a month ago, I had filled out a form on the book company website pretending to be a teacher to see if I could get the book for free. I have done these before, and they never work, so I was just doing it for fun. My answers were absurd, with a fake name, institution, etc, and I thought it would eventually take me to a page with more security where I would have to provide proof of identification, but the form suddenly ended and it was submitted. I had completely forgotten about it, and there were no updates in my email about the book, whether my request was approved or whether the book was shipped. I still have a feeling that this company is likely the one who sent me the book. So, my question is, what do I do with the book? I didn't mean to get it like that, like I didn't think the form would work, but now that I have it, is it permissible to sell it?