Answer
$x=100$ should be excluded;
Inoculating all population is not possible;
Work Step by Step
We are given the function:
$$f(x)=\dfrac{130x}{100-x}.\tag1$$
Because $x$ represents a percent of the population, it means $0\leq x\leq 100$. The rational function is defined for all positive $x$ except the zero of the denominator:
$$100-x=0\Rightarrow x=100.$$
So the only value of $x$ that should be excluded from the rational function's domain is $100$. The domain is:
$$[0,100).$$
When $x$ approaches $100$ from the left, the value $f(x)$ increases indefinitely (the graph has a vertical asymptote $x=100$), so the cost model indicates that we cannot inoculate all the population against the flu.
