Dependency 1: a, c → b, d Left side (a, c)

Since (a, c) functionally determines b and d, its closure includes attributes {a, c, b, d} — that is, all attributes in R.

Therefore, (a, c) is a superkey.

Conclusion: Because the left side is a superkey, this dependency complies with 3NF.

🔹 Dependency 2: a, d → b Right side (b)

Although (a, d) is not a superkey, the right side b is a prime attribute (part of the primary key (a, b)).

Conclusion: Since b is prime, this dependency also complies with 3NF.