The frequency distribution of order lead time at Ecommerce.com from Exercise 18 is repeated below.
Lead Time (days) Frequency
0 up to 5 .......... 6
5 up to 10.......... 7
10 up to 15.......... 12
15 up to 20.......... 8
20 up to 25.......... 7
Total........... 40

a. How many orders were filled in less than 10 days? In less than 15 days?
b. Convert the frequency distribution to a cumulative frequency distribution.
c. Develop a cumulative frequency polygon.
d. About 60% of the orders were filled in less than how many days?