Dear Hexin,

 Please consult

https://sites.math.rutgers.edu/~zeilberg/Hist21/q2S.pdf

for the full solutions.

You got 10 points (out of 10). 

In #4 you did not explain (and what youahd in the left is wrong), but this time I didn't take points off.



 Best wishes,

   Dr. Z.

P.S. Please name your attachment q2HexinBi.pdf . You gave it a different name and I almost missed it.