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# Need Help in Finding Minimal Keys in Relationship Schemas

Am new to database systems and am looking for help in regards to finding minimal keys in a relationship schema. I hope that those reading this post can perhaps help break down the various questions shown below. In the following questions, I am required to list all minimal keys valid within a schema as well as list all derivations of functional dependencies that lead to the identification of minimal superkeys. R(A, B, C, D, E) i) A -> B, C -> D, E -> A For this question I am able to discern that: if A -> B and E -> A then through union rule, A -> BE. But this alone is not enough as from what I understand, a minimal superkey must cover an entire relationship schema. I am unsure on how I can find the link between C -> D and A -> BE. Am suspecting that union rule have to be used but am not sure on how. ii) A -> B, B -> CD, C -> E, E -> AC For this question, I can only discern that: if A -> B and B -> CD then through transitivity rule, A -> CD Any help will be appreciated.