Hi tutors, can I please get your help with the following question?

The pdf of grades in a TA session quiz follows a normal distribution with=75 and =7. Marie scored 80 in this session's exam.

Dave took the exam in another TA session which had a pdf of grades normally distributed with =80 and =4. He got 85.

(a) Who did better in the exam? What is the reasoning, and numbers to support the answer and please explain how you get them.

(b) If we randomly select 5 students from Marie's TA session, what is the probability that 3 of them did better than Marie? Please show me how you find the answer to this and what assumptions you are making. Provide numbers that support your answer and show me how you get them.