Sets - General Questions

Which statement creates an empty set?

What is the output of the following code?

s = {3, 1, 2}
s.add(2)
s.discard(10)
print(sorted(s))

What is the output of the following code?

fs = frozenset([1, 2, 2])
print(len(fs), type(fs).__name__)

What is the output of the following code?

a = {1, 2, 3}
a &= {2, 3, 5}
print(sorted(a))

What is the output of the following code?

a = {1, 2, 3}
b = {2, 3, 4}
print(sorted(a - b), sorted(a ^ b))