Persons with levels of total cholesterol above 240 mg/dl. are at risk for heart disease. For a particular population, the mean total cholesterol level is 170 mg/dl. and the standard deviation is 30 mg/dl. (a) If we assume that cholesterol levels are normally distributed, what percent of this population are at risk for heart disease? Explain your values and show your work. (b) A pharmacologist aims to recruit individuals from this population with cholesterol levels between 146 and 194 mg/dL. Assuming normality, what is the probability (in decimal form) of randomly selecting an individual in this range? Show all of your work and assumptions. Use 4 places behind the decimal point.