In April, Frieda pays $2 apiece for eggs and $1 apiece for sodas. Her income is $40.

Question:

In April, Frieda pays $2 apiece for eggs and $1 apiece for sodas. Her income is $40. She buys 18 eggs and 4 sodas. In May, Frieda pays $1 apiece for eggs and $2 apiece for sodas. Her income is $40. She buys 16 eggs and 12 sodas.
a. In which month is Frieda happier?
b. Are eggs a normal or an inferior good for Frieda?