Choice function

[SimonD]

Hi! I'm kinda stuck with this question:

Recall arrow's axiom of choice consistency AA (2) and chernoff's axiom of choice consistency WA (3). Construct a choice function that satisfies WA while violates AA.

[Amit Goyal]

Suppose the choice rule C(.) is over subsets of X = {a, b, c}, and is given by:
C({a}) = {a}
C({b}) = {b}
C({c}) = {c}
C({a,b}) = {a,b}
C({a,c}) = {a,c}
C({b,c}) = {b,c}
C({a,b,c}) = {a}

Notice that {a,c} ⊂ {a,b,c}, but {a,c} ∩ C({a,b,c}) = {a} is not equal to C({a,c}). So, it violates AA.
Check yourself that this rule does not violate WA.

[RichaS]

Hey, where is this question from?