Rough calcs

Just trying to put a value on this lump of dirt. A few assumptions but the following gives me some perspective. According to the release. IM reckons the inferred resource contains 14.2 billion pounds of Zn and 2.1 billion pounds of Pb. Assuming a 70% conversion from inferred to bankable reserve gives 10.65 billion lbs Zn and 1.57 billion lbs Pb. Once again assuming 75% recovery for both Zn and Pb gives 8 billion lbs Zn and 1.2 billion lbs Pb. Present price Zn US$0.90/lb. Gives US$7.2 billion or A$10 billion. You can add another billion for Pb. Given that all the necessary infrastructure is already in place for transport and export, this gives plenty of wriggle room for development.
I have made some broad assumptions with these calcs and would welcome input from those who are skilled in this area.
The above are my thoughts and calcs and in no way should be used for investment purposes.
Just one typo, I assumed a 75% conversion from inferred to bankable.