(a) Suppose that there is an initial amount A0A0 of a substance and that it decays at exponential rate so that only 65% of the substance remains after two hours. Find the time tt in hours when only 50% of the initial amount remains.

(b) Find with verification the dimensions of the rectangle of largest area such that its top two vertices lie along the parabola y=9?x2y=9?x2 and its bottom two vertices lie along the xx-axis.

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(a) Suppose that there is an initial amount A0 of a substance and that it decays at exponential rate so that only 65% of the substance remains after two hours. Find the timet in hours when only 50% of the initial amount remains. (b) Find with verification the dimensions of the rectangle of largest area 2 such that its top two vertices lie along the parabola y = 9 a: and its bottom two vertices lie along the maxis