12. (Bonus III] points) We inuoduce two equations in the class: Productivity=0utputsfinpt1ts, Productivity growth: (current productivity-previous productivityjiprevious productivity. Please prove the following formula: If inputs increase by X% and outputs increase by Y%, then the 9&3 productivity growth is: 1 +Y% l + X 996 instead of a special input and output). 1. (Note: you should prove that this formula is correct for any common inputs and outputs