In question 5, the  most cruical thought is to find the relationship between each block. We know if we want to find the sum of something, we use a pattern to express this relationship by writing the general formule.  By finding the general formule, we can use the thought of limit to find the extreme value, such as when the last term is infinity. We could use the formule or equation to find it. Also, we should know, in reality, many extreme situations are assumed by us. So, it is impossible to really find the exact value for the infinity term .( Which means we can find someting that still break the rule.)