A boy grips a bar and pulls his body upward until his chin is in line with the bar. He lifts himself by $40\,\text{cm}$ in $0.5\,\text{s}$. The boy’s weight is $500\,\text{N}$. What average power does he produce while lifting himself?
- A$40\,\text{W}$
- B$400\,\text{W}$
- C$4000\,\text{W}$
- D$40\,000\,\text{W}$