Q: In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.
Problem: a man walking at the speed of 4 kmph crosses a square field diagonally in 3 minutes . the area of the field is :
Options: ['a ) 18000 m 2', 'b ) 20000 m 2', 'c ) 19000 m 2', 'd ) 25000 m 2', 'e ) 15000 m 2']
A:
b