Lab-5 Incremental Costs

Question:

In question 3 are we solving for the incremental cost and payback for option A or option B? I thought it was option B because the incremental cost is provided in the question. However, in question 4 it says "1) You've already calculated the construction "costs" in these two units for the two options. 2) Calculate the incremental "cost" for implementing the "green" strategy in these units". Do the "costs" refer to the CO2 and GHG emissions? And why do we have to calculate the incremental cost for the green option if it's provided in question 3?

Answer:

In Question 3 You are given the amount of rainwater that is saved by using Option-B compared to Option-A.  That allows you to calculate the incremental dollar saving in operation.

In question 4 you are indeed asked to calculated incremental cost in units other than dollars – GHG and energy. 

Please read the other posts to get ideas why calculating costs (and thus paybacks) in multiple units can be worthwhile.