Exercise 1. This software checks the validity of a Postal Service money order number. Use it to verify that 39539881642 is valid. Now enter the same number with one digit incorrect. Was the error detected? Enter the number with the 9 in position 2 replaced with a 0. Was the error detected? Explain why or why not. Enter the number with two digits transposed. Was the error detected? Explain why or why not.

Please enter all 11 digits or the first 10 digits here: