Carcass wrote:

The figure above shows an example of a 4-digit customer identification code. If the digits in the code must appear in descending numerical order and no digit can be used more than once, what is the difference between largest and smallest possible codes?
A. 6666
B. 5555
C. 5432
D. 4444
E. 1111
9876 is the biggest code that meets the given conditions
3210 is the smallest code that meets the given conditions
Difference = 9876 - 3210 = 6666
Answer: A