9. EXTRA CREDIT A hash function H : { 0, 1 }n { 0, 1 )" maps a bit string of length n to a bit string of length k. Hash functions are used to give a short label to a long string. The set of all "collisions" with a given string s defines an equivalence class for a given hash function H, that is: (a) What is the average cardinality of the equivalence classes [s in terms of n and ren> k?10 pointsl Replace this text with your answer. (b) What is the probability for any two random bit strings from s,t e 0,1)n that slt? 10 points IH Replace this text with your