The formula \(\rm PI=\dfrac{Y}{Yn}\div\dfrac{T}{Tn}\) where PI = Agriculture Productivity Index ; Y= Total production of selected crops in unit Area; Yn= Total production of same selected crops at national level; T=Total cropped area of the unit ; Tn = Total cropped area at national scale. Who applied this formula for measuring agricultural productivity levels ?
1. Bhatia
2. Enyedi
3. Weaver
4. Shafi