Solution
= Solution
<First-come-first-served disk scheduling> follows the arrival order:
``
133 -> 76 -> 157 -> 91 -> 142 -> 97 -> 135 -> 112 -> 23
``
The total <seek distance> is
$$
\boxed{57+81+66+51+45+38+23+89=450\text{ tracks}.}
$$
The initial position is 133; the earlier completed request at 135 is used to determine direction for the elevator policy, not added again to this total.