A box contains three cards. On one card there is a sun, on another card there is a question mark, and on the third card there is an apple.

Two cards are to be selected at random without replacement.

(a) Determine the number of sample points in the sample space. 

(b) Construct a tree diagram and list the sample space. 

Determine the probability that

(c) Two cards containing apples are selected.

(d) A card containing a sun and then a card containing a question mark are selected.

(e) At least one card that contains an apple is selected.

Use the counting principle to determine the answer to part (a). Assume that each event is equally likely to occur.