One student suggested the series \(1+ \tfrac{1}{2}+ \tfrac{1}{4}+ \tfrac{1}{8}+ \tfrac{1}{16}+\dotsb\) for part (a) because she knew that its sum is \(2\). Here is some of her work for part (c).

One student suggested the series \(1+ \tfrac{1}{2}+ \tfrac{1}{4}+ \tfrac{1}{8}+ \tfrac{1}{16}+\dotsb\) for part (a) because she knew that its sum is \(2\). Here is some of her work for part (c).