Raj stands in a corner of his square farm. Angle of elevation of a scarecrow placed in diagonally opposite corner is 60°. He starts walking backwards in a straight line and after 80ft he realizes that angle of elevation of the scarecrow now is 30°. What is area of the field?

• A. 600 sq.ft.
• B. 0 sq.ft.
• C. $\frac{{40}}{{\sqrt 2 }}$$ sq.ft.
• D. 00 sq.ft.