Suppose that Ted is given a voucher for which none of the last five hex digits can be read. a. Without the wildcard feature, how many guesses must Ted make, on average, to recover the last five hex...

Suppose that Ted is given a voucher for which none of the last five hex digits can be read.

a. Without the wildcard feature, how many guesses must Ted make, on average, to recover the last five hex digits of this particular voucher?

b. Using the wildcard feature, how many guesses, on average, must Ted make to recover the last 5 hex digits of this voucher?

c. How could Dave, a dishonest teller, exploit the wildcard feature to cheat the system?

d. What is the risk for Dave? That is, how might Dave get caught under the current system?

e. Modify the current system so that it allows tellers to securely and efficiently deal with vouchers that fail to scan automatically, but also makes it impossible (or at least more difficult) for Dave to cheat the system.