Suppose that a random variable X has the following moment generating function, < ¼/7. MX(t) = = (1-9t)−7, t< (a) Find the mean of X. (b) Find the variance of X.

Answer part a of the following question. Show work. Let Y > 0 be a continuous random variable representing time from regimen start to bone-marrow transplant. Everyone does not survive long enough to get the transplant. Let X > 0 be a continuous random variable representing time from regimen start to death. We can assume X ⊥ Y and model time to death as X ∼ Exp(rate = θ) and time to transplant as Y ∼ Exp(rate = µ). Where Exp(rate = λ) denotes the exponential distribution with density f(z | λ) = λe−λz for z > 0 and 0 elsewhere - with λ > 0. a.) Compute the probability that a patient receives transplant before they pass away (die) by integrating over the joint density fxy.

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