How do the representations in Exercises 14 and 15 improve the error detection over a simple check digit? Given the following numbers, what would be the additional digits if the units digit of the sum...

How do the representations in Exercises 14 and 15 improve the error detection over a simple check digit?

Given the following numbers, what would be the additional digits if the units digit of the sum of the odd digits is used along with the check digit?

a. 1066

b. 1498

c. 1668

d. 2001

e. 4040