:3. 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.

The percentage who smoked ten cigarettes or less per day is
closest to

 a. 1.5%
 b. 15%
 c. 30%
 d. 50%
 e. 70%