use strict;
use warnings;

my ($raw, $capacity, $unassigned);
while (<DATA>) {
    $raw = $1 if m/Raw capacity: (\d+\.\d+) GB/;
    if (m/Mode: Unassigned/) {
        $capacity += $raw;
        $unassigned++;
    }
}

print int ($capacity / $unassigned * 1000 + .5) / 1000;

__DATA__
Drive at Tray 0, Slot 5
Raw capacity: 68.366 GB
Usable capacity: 67.866 GB
Current data rate: 2 Gbps
Product ID: ST373453FC
Mode: Unassigned
Drive at Tray 0, Slot 5
Raw capacity: 48.366 GB
Usable capacity: 67.866 GB
Current data rate: 2 Gbps
Product ID: ST373453FC
Mode: Assigned
Drive at Tray 0, Slot 5
Raw capacity: 88.366 GB
Usable capacity: 67.866 GB
Current data rate: 2 Gbps
Product ID: ST373453FC
Mode: Unassigned