a.) Altinbas University with 8000 students has a scheme according to which each student buys a Christmas gift and the gifts are then distributed at random to the students. What is the probability that a student gets his or her own gift?

b.) A coin with Heads probability p is tossed repeatedly. What is the expected number of tosses needed to get k successive heads? (hint: 'succesive' means if an outcome is Tails during the experiment, then we have to start from the beginning)