試題詳解

169. An insurance company will cover losses incurred from tornadoes in a single calendar year. However, the insurer will only cover losses for a maximum of three separate tornadoes during this timeframe. Let X be the number of tornadoes that result in at least 50 million in losses, and let Y be the total number of tornadoes. The joint probability function for X and Y is
  
 where c is a constant.
Calculate the expected number of tornadoes that result in fewer than 50 million in losses.
(A) 0.19
(B) 0.28
(C) 0.76
(D) 1.00
(E) 1.10