2.16: Password selection from mixed characters
A 7-character password is to be selected from the 12 characters shown in the table. Each character may be used only once.
| Characters | |
|---|---|
| Upper-case letters | A, B, C, D |
| Lower-case letters | e, f, g, h |
| Digits | 1, 2, 3, 4 |
(i)[1]
Find the number of different passwords if there are no restrictions.
(ii)[1]
Find the number of different passwords that start with a digit.
(iii)[3]
Find the number of different passwords that contain 4 upper-case letters and 3 lower-case letters such that all the upper-case letters are together and all the lower-case letters are together.