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5. (a) (10) A rectangle with sides parallel to the r axis and y axis, and symmetric with respect to the y axis, is to be inscribed in the ellipse 4 + y' = 1. Find the maximum possible area A of the rectangle. Support your answer. (b) (10) The amount of a given radioactive substance today is 8 grams. After 10 years, the amount remaining is 6 grams. Find the half-life of the substance. Show your work. H