The price-earnings ratios of a sample of stocks have a mean value of 12.5 and a standard deviation of 1. If the ratios have a mound-shaped, symmetric distribution, using the Empirical (68-95-99.7) Rule, what can we say about the proportion of ratios that fall between:
a. 11.5 and 15.5?

b. 10.5 and 14.5?

c. In what interval would we expect to find 99.7% of price-earnings ratios?