Consider the set of integer numbers from 0 to 9, that is {0, 1,
2, 3, 4, 5, 6, 7, 8, 9}. Bob wishes to use these numbers to create
a 7-digit password to secure his new laptop. Note that each number
can appear in any position (for example, 0 can be the first number
in the password). (a) Find the number of 7-digit passwords that are
possible. (b) Find the number of 7-digit passwords with distinct
digits. (c) Find...