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A certain store sells only T-shirts. Let the random variable X represent the number of T-shirts bought from the store on any day, with a mean of 75 and a standard deviation of 20. Let the random variable Y be the total revenue from this store on a randomly selected day. If the store charges $15 per T-shirt, what are the mean and standard deviation of Y

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Answer:


(a)\ \mu_y = 1125


(b)\ \sigma_y = 300

Explanation:

Given


\mu_x = 75 -- Mean of T-shirts


\sigma_x = 20 -- Standard deviation of T-shirts


Rate = \$ 15

Solving (a): The mean of the revenue
(\mu_y)

To solve this, we use:


\mu_y = Rate * \mu_x\\

This gives:


\mu_y = 15 * 75


\mu_y = 1125

Solving (b): The standard deviation of the revenue
(\sigma_y)

To solve this, we use:


\sigma_y = √(Rate^2 * \sigma_2^2)

This gives:


\sigma_y = √(15^2 * 20^2)


\sigma_y = √(90000)


\sigma_y = 300

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