added google sheet to staking

ethereum-roadmap/serenity-phases/eth-2.0-economics.md

@@ -106,3 +106,5 @@ More traditional investment alternatives such as bonds, certificates of deposit,
 **Alternative Staking Coins**  
 There is over [500 alternative PoS coins](https://masternodes.online/), with a reward structure. Why stake ETH, when one can earn more, with potentially less infrastructure and risk, on another coin?
 
+## Spreadsheet Example
+Click [here](https://docs.google.com/spreadsheets/d/1SZBJsTHBFmRlo6aLZ0ex_bnTO3MqQrsZK9yLWqL4r68/edit?usp=sharing) to see calucations of network and personal staking variables given the latest spec.