Need help with Exercise 3.2.2 only i) (You need to resolve questions a, b, c as per 3.2.1)

Exercise 3.2.1: Consider a relation with schema R(A, B,C, D) and FD's AB C, C D, and D A a) What are all the nontrivial FD's that follow from the given FD's? You should restrict yourself to FD's with single attributes on the right side. b) What are all the keys of R? c) What are all the superkeys for R that are not keys? Exercise 3.2.2: Repeat Exercise 3.2.1 for the following schemas and sets of FD's: i) S(A, B,C,D) with FD's A B. B C, and B D ii) T(A, B,C,D) with FD's AB C, BC D, CD A, and AD B iii) U(A,B,C,D) with FD's A B, B C, C D, and D A