A man with a mass of $75\,\text{kg}$ runs up a staircase made up of $30$ steps. Each step has a height of $20\,\text{cm}$. He takes $7.0\,\text{s}$ to run from the bottom of the staircase to the top. What is the average rate of increase in the man's gravitational potential energy?
- A$64\,\text{W}$
- B$450\,\text{W}$
- C$630\,\text{W}$
- D$4400\,\text{W}$