An investor is considering buying bonds being issued by one of three different not-for-profit healthcare systems and has the following information from the financial statements. From the information provided which of the healthcare systems appear to be the most financial sound and thus the best investment opportunity?

A) Healthcare System A: Operating margin 2.2%, Days cash on hand: 120; Age of plan, years: 11.5; Debt service coverage ratio: 2.8

B) Healthcare System B: Operating margin 4.0%, Days cash on hand: 110; Age of plan, years: 10; Debt service coverage ratio: 4.5

C) Healthcare System C: Operating margin 4.5%, Days cash on hand: 237; Age of plan, years: 8.5; Debt service coverage ratio: 5.6