18. Stop-One.com, a large Internet retailer, is studying the lead time (elapsed time between when an order is placed and when it is filled) for a sample of recent orders. The lead times are reported in days.

Lead Time (days) Frequency 0 to under 5 6 5 to under 10 7 10 to under 15 12 15 to under 20 8 20 to under 25 7 Total 40

a. How many orders were studied?

b. What is the midpoint of the first class?

c. What are the coordinates of the first class for a frequency polygon?

d. Draw a histogram.

e. Draw a frequency polygon.

f. Interpret the lead times using the two charts.