A mother decides to teach her son about a letter each day of the week. She will choose a letter from the name of the day. For example, on Saturday she might teach about the letter Sor the letter U, but not the letter M.

1. Who letters are possible to teach using this method? (There are 15.)

2. What are 4 letters that can't be taught using this method?

3. On TUESDAY, the mother writes the word on a piece of paper and cuts it up so that each letter is on a separate piece of paper. She mixes up the papers and picks one. What is the probability that she will choose the piece of paper with the letter Y? Explain your reasoning