Can you please explain how to get these solutions

Problem 2 (3 points, 1 pt each): How many elements does each of these sets have where a and b are distinct elements? (110 represents the power set.) SOLUTION: 8 (25) b) P(o,a, a,fa!) SOLUTION: 16 (-24) e) P (P ()) SOLUTION: 2 (P () has one element so its power set has 2 elements)