The U.S. Postal Service is to deliver a letter to a certain postal ZIP 4 code. Find the probability that the ZIP 4 code is corre
ct if the sender (a) randomly chooses the code, (b) knows the five-digit code but must randomly choose the last four digits, and (c) knows the five-digit code and the first two digits of the plus 4 code.
If the slope was a horizontal line, then we could say y=2, however, it is only going through the x-axis so it would be x=2, but in terms of y it is undefined.
