Add discussion of feasibility considerations in "solving right problem"

[nickeubank]

Talk about how often best to start by specifying ideal, then work back to feasible. Lot of student questions about this.

https://github.com/nickeubank/ds4humans/blob/main/30_questions/00_solving_the_right_problem.md

[joshclinton]

Perhaps talk about what you could do if you had complete control over everything. i.e., randomization, etc. Then compare that to what type of variation you actually observe and think about how that departs from the ideal.

[nickeubank]

Yeah, exactly!