Problem 5. There are four snipers ring at the enemy from hidden positions. The enemy is constantly searching for the snipers' locations, and when a sniper's location is discovered, she is killed in a hail of bullets. Assume that the snipers begin their work at the same time and that the snipers' \"lifetimes\" (the time until they are discovered and killed) are i.i.d. exponential random variables with a mean of 6 hours. (a) (4%, NWR) Find the mean of the time until the last sniper dies. (b) (4%, NWR) Find the variance of the time until the last sniper dies. This uses the general results on page 12 of notes'7.pdf. Plugging k = 4 into these results is all that is needed. No other work is required. (c) (8%) The snipers are killed off one by one. Assume that, while I: snipers remain alive, they kill the enemy soldiers at an average rate of CW deaths per hour. (0 is an arbitrary positive value.) What is the expected value of the total number of enemy soldiers killed by the four snipers? This is similar to exercise C4