83. Six hundred adult Americans were asked by telephone poll, "What do you think constitutes a middle-class income?" The results are in Table 2.69. Also, include left endpoint, but not the right endpoint.

Salary ($) Relative frequency

<20,000 0.02

20,000-25,000 0.09

25,000-30,000 0.19

30,00-40,000 0.26

40,000-50,000 0.18

50,000-75000 0.17

75000-99,999 0.02

100,000+ 0.01

a. What percentage of the survey answered "not sure"? b. What percentage think that middle-class is from $25,000 to $50,000? c. Construct a histogram of the data. i. Should all bars have the same width, based on the data? Why or why not? ii. How should the <20,000 and the 100,000+ intervals be handled? Why? d. Find the 40th and 80th percentiles e. Construct a bar graph of the data