Hi Mvanle,
What I used was just a most common method call PE valuation.
Go to for example
http://en.wikipedia.org/wiki/Stock_valuation
and read
"The valuation's fair price is simply estimated earnings times target P/E."
The factor 10 is the "target P/E". Historically GTP's P/E usually much less then 10, so applying 10 to this factor is lenient.
