The blood cholesterol levels in 14-year-old boys are approximately normally distributed. Within this curve, 99.7% of the levels, centered about the mean, are between 75 and 255 milligrams of...

The blood cholesterol levels in 14-year-old boys are approximately normally distributed. Within this curve, 99.7% of the levels, centered about the mean, are between 75 and 255 milligrams of cholesterol per deciliter of blood. The standard deviation is 30 milligrams of cholesterol. Use this information to estimate the mean blood cholesterol level in 14-year-old boys. Approximate the probability that a boy has a cholesterol level less than 135. Explain how you determined your answers.