Final answer:
The average metabolic rate of a man who metabolizes 10,500 kJ of food energy in one day is 121.5 W.
Step-by-step explanation:
To calculate the average metabolic rate in watts, we need to convert the food energy from kilojoules (kJ) to joules (J) and then divide it by the number of seconds in a day. 10,500 kJ is equivalent to 10,500,000 J. There are 86,400 seconds in a day, so the average metabolic rate in watts is 121.5 W.