[填空题]
Water is pumped from a river basin into anf z64 02lephec irriga mzhxwjc9n3v .rn:t2/ted field at a rate of r=\fracjrnch3m .zx 9vn/w2 :t{t^{2}}{25} where r is measured in cubic metres of water per minute and t is the time measured in minutes. The graph of this is shown below.
1. Write down an integral that represents the area of the shaded region. It is A =$\int_{0}^{60} \frac{t^{2}}{a} \mathrm{~d} t$ ;a= .
2. 1. Find the area of the shaded region is m$^2$.
2. Interpret the meaning of the shaded area in the context of this question.
3. Find the number of minutes it takes to pump 500 $\mathrm{~m}^{3}$ of water into the field.
m≈ min (one deciaml pleaces).
