Amazon.com, Inc., reported the following financial data $($amounts in millions$)$:

Calculate ROA and ROCE for $2016$ using average balances for any balance sheet amounts. The statement which best explains the difference between ROA and ROCE for $2016$ is

a$.$ ROA is affected by the asset base and is lower than ROCE due to a large amount of fixed assets.

b$.$ ROCE is higher than ROA because no preferred stock is outstanding.

c$.$ ROCE is higher than ROA because of high leverage.

d$.$ ROA is lower than ROCE because interest expense is so high.