The table compares how exercise changes the rate and depth of breathing. At rest: breathing rate 12 breaths per minute, volume of each breath $500\,\text{cm}^3$. After exercise: breathing rate 24 breaths per minute, volume of each breath $1000\,\text{cm}^3$. What is the increase in the volume of air exchanged per minute after exercise, compared with at rest?
- A$1000\,\text{cm}^3$
- B$6000\,\text{cm}^3$
- C$18\,000\,\text{cm}^3$
- D$24\,000\,\text{cm}^3$