Logic Riddles

Question: Two is company and 3 is a crowd. What is 4 and 5?

Question: A mother is 21 years older than her child. In 6 years the mother will be 5 times older than her baby.

Where is the father?

Question: Using 3 periods (.) and 1 question mark (?) make this a logical and grammatically correct sentence:

"That that is is that that is not is not is that it it is"

Question: Mary gets in the shower, but surprisingly her hair is not wet when she gets out. How is this possible?

Question: Is an older one-hundred dollar bill worth more than a newer one?