I used your figures of an historically 'normal' STO market cap between 09 and 11.
31/12/ 09 31 /12/10 31/12/11
$11.721 bill $11.506 bill $11.560 bill
I used the median of $11.5b compared with the current mc of $9.23b and chose not to adjust for inflation. The predicted SP I came up with is $5.52.
For those interested in the simple maths, it is 11.5/9.23 x 4.43 (current share price)