Dear Karan,

 Please consult

https://sites.math.rutgers.edu/~zeilberg/Hist21/q8S.pdf

for the full solutions.

You got 7 points (out of 10). Here is what you got wrong:

#1: -1 points (Euler derived it)

#2: -1 points (his father was a day laborer, perhaps he was also a butcher, but you got this from the internet, and you are only supposed to use the book)

#4: -1 point (did not part d) (In (a)  you confused "associativity" with "commutativity" but I did not take points of for this)


 Best wishes,

   Dr. Z.