The clearness index was determined for the skies over Baghdad for each of the 365 days during a particular year (“Contribution to the Study of the Solar Radiation Climate of the Baghdad Environment,” Solar Energy [1990]: 7–12). The accompanying table summarizes the resulting data:

a. Determine the relative frequencies and draw the corresponding histogram. (Be careful here—the intervals do not all have the same width.)

b. Cloudy days are those with a clearness index smaller than 0.35. What proportion of the days was cloudy?

c. Clear days are those for which the index is at least 0.65. What proportion of the days was clear?

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Clearness Index 0.15 to <0.25 0.25 to <0.35 0.35 to <0.45 0.45 to <0.50 0.50 to <0.55 0.55 to <0.60 0.60 to <0.65 0.65 to <0.70 0.70 to <0.75 Number of Days (frequency) 8 14 28 24 39 51 106 84 11