Wageweb exhibits salary data obtained from surveys. It provides compensation information on more than 170 benchmark positions, including finance positions. It recently reported that salaries of chief finance officers (CFOs) ranged from $127,735 to $209,981 (before bonuses). Suppose the following data represent a sample of the annual salaries for 25 CFOs. Assume that data are in thousands of dollars.

a. Using 11 classes, construct a cumulative frequency distribution.
b. Determine the proportion of CFO salaries that are at least $175,000.
c. Determine the proportion of CFO salaries that are less than $205,000 and at least $135,000.