7.76 The paper referenced in the previous exercise also included data on left atrial diameter for children who were considered overweight. For these children, left atrial diameter was approximately normally distributed with a mean of 28 mm and a standard deviation of 4.7 mm.

a. Approximately what proportion of overweight children has left atrial diameters less than 25 mm?

b. Approximately what proportion of overweight children has left atrial diameters greater than 32 mm?

c. Approximately what proportion of overweight children has left atrial diameters between 25 and 30 mm?

d. What proportion of overweight children has left atrial diameters greater than the mean for healthy children?