How to calculate tax.... its urgent pls......

i have one query regarding income tax calculation.

one of person purchased agriculture land for rs.500000 and convert said land to NA, after 4 year it is sold for rs. 3 cr.

note: 1.land converted to NA after 3 years from the date of purchase.

           2. land situated in small village, poputation of the village is 12000 people.

how to calculate tax in above situation ? and under what section ?