Suppose that the life expectancy X of each member of a certain group of people is an r.v. having the Negative Exponential distribution with parameter l = 1/50 (years). For an individual from the group in question, compute the probability that
i) He will survive to retire at 65;
ii) He will live to be at least 70 years old, given that he just celebrated his 40th birthday;
iii) For what value of c, P(X > c) = 1?