Answer
See below
Work Step by Step
From part a, we found $\sum^{\infty}_{n=0} 24\times0.7^n$
We will just calculate one distance. Hence, we have:
$$12+\sum^{\infty}_{n=0} 24\times0.7^n\\=12+\frac{24}{1-0.7}\\=12+\frac{24}{0.3}\\=12+80\\=92$$