Solution
= Solution
The first four letters may be permuted in $4!$ ways and the last two in $2!$ ways without changing this partition. The <multiplication principle> therefore gives
$$
\boxed{4!\,2!=48}.
$$
= Solution
The first four letters may be permuted in $4!$ ways and the last two in $2!$ ways without changing this partition. The <multiplication principle> therefore gives
$$
\boxed{4!\,2!=48}.
$$