Final answer:
a. True, b. True, c. False, d. False, e. False, f. False
Step-by-step explanation:
a. True: A set is always a subset of itself. Therefore, a⊆a is true.
b. True: The empty set (∅) is a subset of every set. Therefore, ∅⊆∅ is true.
c. False: The empty set (∅) is not a proper subset of itself. Therefore, ∅⊂∅ is false.
d. False: The empty set (∅) is not a proper subset of itself. Therefore, ∅⊂∅ is false.
e. False: The empty set (∅) is not a proper subset of itself. Therefore, ∅⊂∅ is false.
f. False: The set {a,b} is not a subset of the power set of {a,b}. Therefore, a⊆℘{a,b} is fals