#### Answer

$27600$ and
$35152$

#### Work Step by Step

The call letters of a radio
station must have 4 letters. The first letter must be a K or a W.
How many different station call letters can be
made if repetitions are not allowed?
The first letter has 2 choices, the second one 25, third 24, and forth 23,
so the total is $2\times25\times24\times23=27600$
If repetitions are allowed?
In this case, the first letter has 2 choices, the second one 26, third 26, and forth 26,
so the total is $2\times26\times26\times26=35152$