2.70 Lumber Rights A company interested in lumbering rights for a certain tract of slash pine trees is told that the mean diameter of these trees is 35 cm with a standard deviation of 7 cm. Assume the distri- bution of diameters is roughly mound-shaped.

a. What fraction of the trees will have diameters between 21 and 55 centimetres?

b. What fraction of the trees will have diameters greater than 43 cm?