:3b. In a Public Health Service Study of 1964, a histogram was plotted showing the number of cigarettes per day smoked by each subject (male, current smokers), as shown in diagram ? on page ? of the test. The density is marked in parentheses. The class intervals include the right endpoint, not the left.
a. 1.5% b. 15% c. 30% d. 50% e. 70%
(There are twenty cigarettes in a pack.)