The rational expression
$$\frac{130 x}{100-x}$$
describes the cost, in millions of dollars, to inoculate $x$ percent of the population against a particular strain of flu.
a. Evaluate the expression for $x=40, x=80,$ and $x=90$ . Describe the meaning of each evaluation in terms of percentage inoculated and cost.
b. For what value of x is the expression undefined?
c. What happens to the cost as x approaches 100%? How can you interpret this observation?