On the surface cost benefit analysis seems straightforward

The steps taken to evaluate each benefit and cost can become quite complicated. In this case, a benefit is defined as anything that increases human well-being, and a cost is anything that decreases it. These definitions and their respective calculations tend to provoke controversy due to the use of valuation.

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom. 

12 is probably the typical age for a first kiss but i think its to young.