Even though the direct costs of malpractice disputes

[haj]

Even though the direct costs of malpractice disputes amounts to a sum lower than one percent of the $541 billion the nation spent on health care last year, doctors say fear of lawsuits plays major role in health-care inflation.
(A) amounts to a sum lower
(B) amounts to less
(C) amounted to less
(D) amounted to lower
(E) amounted to a lower sum

Source: GMAT Prep

I was confused between B and C. I like past tense because of the reference to 'last year' , but I like present tense because even though the money was spent last year, it still sums up or 'amounts' to 514b in the present.
Please help.

[StaceyKoprince]

Check out the subject-verb agreement issue first.

The subject is "costs" (non-underlined, so can't be changed) and that's paired with "amounts." Even though the costs amounts to...? Nope. Eliminate A and B.

So that eliminates B for you - C it is.