Regarding the last bullet ("What if I told you that..."):
At the end of the first sentence of the prompt, should we clarify that "and the key I used was 10 characters long, without repeated characters. That way, the math of part 2 of the answer will be correct. The other option is to have the math read 26^10, however this allows for keys like AAA, BBB, etc which we established earlier in the worksheet were simple Cesar Ciphers. I would lean towards the latter, as we need to include keys like BDBD that have repeated characters. Sorry, it's the math nerd in me.