The molality of a solution containing 8.1 moles of solute in 4847 g of solvent is

Molality is defined as the number of moles of solute in 1 kg of solvent 
the number of moles of solute - 8.1 mol
mass of solvent - 4847 g
there are 8.1 mol in 4847 g of solvent 
we need to know how many moles are in 1 kg of solvent
therefore number of moles in 1 kg of solvent is - 8.1 mol / 4.847 kg 
molality of solution is - 1.67 mol/kg 

Mass of water is smething that you froma drug test or sum girl ya

Most likely a is the answer - because  you generate   38 atp's but also consume an atp.   each atp gives approx. less than 4 kcal so probably a is the closest answer.