Conduct an extensive Monte Carlo simulation studies to decide what types of bulbs and how many you have to purchase. The following are some sample questions which may help you make a good decision. However, your study should not be limited by those questions. 

(a) What is the expected total lifetime if you decide to bring 3 A bulbs?

What is the probability that the total lifetime of 3 A bulbs exceed 55 hours? What is the total purchasing cost? (b) How will the answers in part (a) be changed if you bring 4 bulbs? Or if you bring B bulbs, C bulbs, or D bulbs? (c) How will the answers in part (b) be changed if you bring 3 A bulbs and 1 B bulb? (d) How will the answers in part (c) be changed if you bring 2 A bulbs, 1 C bulb and 1 D bulb? (e) An open question: what is your recommendation? You are encouraged to conduct more simulation to support your recommendation.