Suppose that 30% of all students who have to buy a text for a particular course want a new copy (the successes!), whereas the other 70% want a used copy. Consider randomly selecting15purchasers.

(a)What are the mean value and standard deviation of the number who want a new copy of the book? (Round your standard deviation to two decimal places.)

mean __________students

standard deviation_________ students

(b)What is the probability that the number who want new copies is more than two standard deviations away from the mean value? (Round your answer to three decimal places.)

(c)The bookstore has10new copies and10used copies in stock. If15people come in one by one to purchase this text, what is the probability that all15will get the type of book they want from current stock? [Hint: LetX= the numberwho want a new copy. For what values ofXwill all15get what they want?] (Round your answer to three decimal places.)

(d)Suppose that new copies cost$150and used copies cost$80. Assume the bookstore currently has 50 new copies and 50 used copies. What is the expected value of total revenue from the sale of the next15copies purchased? [Hint: Leth(X) = the revenuewhenXof the15purchasers want new copies. Express this as a linear function.]

$___________

Indicate what rule of expected value you are using.

E(aX+b) =aE(X).

E(aX+b) =a²E(X)

E(aX+b) =E(X) +b.

E(aX+b) =aE(X) +b