I think it would be kidneys because of the way the question is worded, kidneys are the only things you have 2 of that also is involved in the digestion of foods.
Benzodiazepines are a central nervous system depressant, and have muscle-relaxing properties (such as valium). Opioids may also be considered CNS depressants, but I am not sure that they cause muscle relaxation.
I believe it is Amy's, because you said Amy's target heart rate zone is 140bpm -- 186bpm. Thus, Amy's is higher
