Add Admob Rewarded video Ads to Android

This may need some interface design to handle it.
https://play.google.com/store/apps/details?id=com.aliateck.TaxCalcEG
user will earned 100 points for each video. when user click calculate buttom you will check for balance. each click on calculate cost 30 points when gross selected and 60 points when (net) selected. Thats all.