Suppose that the time T until a type of television set fails is an exponential r.v. with rate 0.2. Recall the probability density function of T, and the cumulative distribution of T.

(a) Find the probability that failure occurs between 3 and 5 years.

(b) If a TV set did not fail in 10 years, what is the chance that it will fail in the next year?

(c) A school buys 10 TV sets. Let N be the number that fail during the first 4 years. Find the distribution of N.

All help greatly appreciated!