Chapter 1.2, Problem 54E

Fish species growth For many species of fish, the weight W is a function of the length L that can be expressed by

$W=W(L)=k{L}^{3}k=\text{constant}$

Suppose that for a particular species k = 0.02, that for this species the length(in centimeters) is a function of the number of years t the fish has been alive, and that this function is given by

$L=L(t)=50-\frac{{(t-20)}^2}{10}0\le t\le 20$

Find $\left(W\cdot L\right)\left(t\right)$ to express W as a function of the age t of the fish.