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I'm not sure why you changed the answer from 2.63E-8 to 2.63E-5. The back of the book has it as 2.63E-8C.
Yes,
I don't understand that either.
Thanks for mentioning this. That was a mistake. I've updated the text answer, although I've left the video alone since it's quite a bit more effort to re-record it, and I'll make a note above the video about the small error.