To do with part a), we are given 4 graphs presenting the change and regularity of Sierpinski carpet. From these graphs, we can see and find the value of each p1,p2,p3, then deduct the general formula. (The whole construction follows the general formula shown in initial several steps)

To do with part b), find the relationship between what we have and what we want. We write the p_n we get from a) in the standard formation of its series type. p_n is the geometric series, and it can be written as  a*q^{n-1}, then just plug it in the relationship we establish.

in part c), we find the limit in we get the answer in part b). To reject the answer in b, we can abandon the  limit which makes area equals 0, so the equation is not satisfied, the requirement of c satisfies.