Dear Armen,

 Please consult

https://sites.math.rutgers.edu/~zeilberg/Hist21/q9S.pdf

for the full solutions.

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

#4  you did do

#5(a) (that  you called #4) was correct

but #5(b) was too sketcy, so you got one point ouf of 3


 Best wishes,

   Dr. Z.