Among the following sets, identify all pairs of equal sets?

[persian52]

1. Among the following sets, identify all pairs of equal sets? What is the cardinality of each one
of the sets?

a) ∅
b) {∅}
c) {{∅}}
d) {∅,{∅}}
e) {∅} \bigcap {{∅}}
f) {{∅},∅}
I would truly appreciate if you explain a bit.
Thank you in advance.
_____________________________________________
my answer:

a) Zero
b) one
c) one
d) two
e) not sure but i think it's two or zero.?
f) two

 

[haruspex]

All correct. For e), what do you think the set is?

 

[persian52]

I believe zero.
btw thank you.

 

[haruspex]

I believe zero.
btw thank you.

Yes, it's null.