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.90 is a radioactive material that decays according to the function A(t) = A0 9" 00244., where A0 is the initial amount present and A is the amount Strontium of 800 grams of strontium-90. present at time t (in years) Assume that a scientist has a sample (a) What is the decay rate of strontium90? ' b) How much strontium90 is left after 40 years? c) When will only 200 grams of strontium90 be left? What is the halflife of strontium-90? )The decay rate of strontium-90 is 2'44 "/0. V e an integer or a decimal. lnclude the negative sign for the decay rate.) LE . b)Appromately [1 grams of strontium90 is left after 40 years. Do not round until the nal answer. Then round to the nearest whole number as needed.)