Draw structural formulas for the alkoxide ion and the alkyl(aryl)bromide that may be used in a williamson synthesis of the ether shown.

Williamson synthesis is the most common way for obtaining ethers, called after its developer Alexander Williamson. It is an organic reaction of forming ethers from an organohalide and an alkoxide. The reaction is carried out according to the SN2 mechanism.

On the attached picture it is shown required alkoxide ion, alkyl(aryl)bromide and the ether that forms from the reactants. 

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.