Assume that total cholesterol levels in U.S. citizens over 20 years of age have a μ of 191 mg/d and a σ of 24.5 mg/dl. What would be the chance of randomly selecting a person from this population who has a total cholesterol level of 191 mg/dl or above?
a. 50%
b. 68%
c. 84%
d. 92%