Answer: The one that fell on its feet.
Explanation: The sinking of the two cows will depend on the pressure exert on the mud.
Pressure is the ratio of force to area.
The one which fell on its side would exert lower pressure because of its larger side of area. While the one that fell on its feet will exert greater pressure because of small area of its feet.
Therefore, the one that fell on its feet will sink furthest into the mud because of the ratio of the force to area of its feet ( pressure) is higher.
