In Example 2 we considered the function $W=f(T, v)$, where $W$ is the wind-chill index, $T$ is the actual temperature, and $v$ is the wind speed. A numerical representation is given in Table 1.
(a) What is the value of $f(-15,40)$ ? What is its meaning?
(b) Describe in words the meaning of the question "For what value of $v$ is $f(-20, v)=-30$ ?" Then answer the question.
(c) Describe in words the meaning of the question "For what value of $T$ is $f(T, 20)=-49 ?^{\prime \prime}$ Then answer the question.
(d) What is the meaning of the function $W=f(-5, v)$ ? Describe the behavior of this function.
(e) What is the meaning of the function $W=f(T, 50)$ ? Describe the behavior of this function.