A took 15 sec. to cross a rectangular field diagonally walking at the rate of speed 52m / min and B took the same time to cross the same field along its sides walking at the rated speed 68 m / min. The area of the field is:

• A. $$30 m^2$$
• B. $$40 m^2$$
• C. $$50 m^2$$
• D. $$60 m^2$$