Find elements of corresponding equivalence relation

Question

Consider A = {a, b, c, d}. For each of given partitions of A, find elements of corresponding equivalence relation:

i) P₁ = {{a, c}, {b, d}}

ii) P₂ = {{a}, {b, c}, {d}}

iii) P₃ = {{a, b}, {c, d)}

iv) P₄ = {{a, b, c}, {d}}

Do any of partitions refine any of others?