Mary has in her wallet three $1 coins, one $2 coin and four coins of 25 ¢. She selects four coins at random from her wallet.

(i) Write down a sample space for the possible selections she can make.

(ii) Express the following events as subsets of the above sample space:

C1: exactly three 25 ¢ coins are selected;

C2: the total value of the coins selected is $2.50;

C3: the total value of the coins selected is $3.50.