average constant cost

例句：

1. 1. The averagetemperature in New York is 59degrees Fahrenheit.
   纽约的平均温度是华氏59度。
2. 2. Theaverage income of a doctor is much higherthan that of a lawyer.
   医生的平均收入远高于律师。
3. 3. The average lifespan for humansis about 75 years.
   人类的平均寿命大约是75岁。