This is a cryptology questions but involves some math theory. I am not sure how to answer it.

2. Let f ER Fn,l, where n > l. What is the expected number of strings 2 E {0, 1} such that x + 1 and f(x) = f(1")? 2. Let f ER Fn,l, where n > l. What is the expected number of strings 2 E {0, 1} such that x + 1 and f(x) = f(1")