question: Q:A randomized controlled trial is conducted to evaluate the relationship between the angiotensin receptor blocker losartan and cardiovascular death in patients with congestive heart failure (diagnosed as ejection fraction < 30%) who are already being treated with an angiotensin-converting enzyme (ACE) inhibitor and a beta blocker. Patients are randomized either to losartan (N = 1500) or placebo (N = 1400). The results of the study show:
  Cardiovascular death No cardiovascular death
  Losartan + ACE inhibitor + beta blocker 300 1200
  Placebo + ACE inhibitor + beta blocker 350 1050
  Based on this information, if 200 patients with congestive heart failure and an ejection fraction < 30% were treated with losartan in addition to an ACE inhibitor and a beta blocker, on average, how many cases of cardiovascular death would be prevented?"? 
  {'A': '20', 'B': '10', 'C': '0.25', 'D': '50', 'E': '0.05'},