4. In a branching process the ospring distribution is given by 1 1 1 P(Z=0)=, P(Z=1)= P(Z=2)=. (a) Find the extinction probability of the process if it starts with a single individual. (b) Find the extinction probability of the process if it starts from 3 individuals. (c) Find the extinction probability of the process started with a single individual conditioned on the event that there are 2 individuals in the rst generation and 10 individuals in the 5th generation