OG 10 : VR : 101 : Even though the direct costs ...

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 a major role in
health-care inflation.

C) amounted to less
D )amounted to lower
E )amounted to a lower sum

For the object of preposition to ( amounted to ..... ) we need a
noun (less) and not a adjective (lower).