Gender guess 13w2days

Hi, i am new to here; I've been stalking and reading threads for a few months but never posted. I did some reading on the nub theory and have looked at countless scans, even taken some of those quizzes, but i can't tell on mine. Don't even know if it's a good enough shot to tell really. How do you know where the spine is??
This is our third and we already have two boys, so I'm really hoping for girl but it looks like a boy to me from this. This was a confirmed twin pregnancy but baby A died at 8wks, i found out at 11 wks both that it was twins and only one. We were looking at everything the tech was scanning just to be sure this one was ok that i never really looked for the nub like i had originally planned to do.
Thanks in advance!
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