Once an individual has been infected with a certain disease, let X represent the time (days) that elapses before the individual becomes infectious. An article proposes a Weibull distribution with a = 2.6, ẞ 1.9, and y = 0.5. [Hint: The two-parameter Weibull distribution can be generalized by introducing a third parameter y, called a threshold or location parameter: replace x in the equation below, α f(x; α, ẞ) = Ba - -(x/B)a X ≥0 X < 0 by x - y and x 20 by x ≥ y.] (a) Calculate P(1 < x < 2). (Round your answer to four decimal places.) 0.3871 (b) Calculate P(X > 1.5). (Round your answer to four decimal places.) 0.8282 (c) What is the 90th percentile of the distribution? (Round your answer to three decimal places.) 3.119 days (d) What are the mean and standard deviation of X? (Round your answers to three decimal places.) mean standard deviation days days