The cost per item at a supermarket follows an exponential distribution. There are many inexpensive items and a few relatively expensive ones. The mean cost per item is $8.00. What is the percentage of items that cost:
A. Less than $5.00 (round to 4 decimal places)
B. More than $9.00 (round to 4 decimal places)
C. Between $6.00 and $8.00 (round to 4 decimal places)
D. Find the 40th percentile. 60% of the supermarket items cost more than what amount?