Counting Elements in Sets: Steps Included

[Madonna M.]

How many elements does each of these sets have where a and b are distinct elements? (with steps please)

a) P({a,b{a,b}})b)P({∅,a,{a},{{a}}})
c)P(P(∅))

*i have tried to solve them but i am a little bit confused...

Thanks in advance :)

 

[haruspex]

Pls post your attempts at solution, including any reasoning.