d. For what value is this equation undefined?

This is the question I am trying to answer, so would it be 100%?

1. The cost, in millions of dollars, to remove x % of pollution in a lake modeled by C=6000/200-2x
a. What is the cost to remove 75% of the pollutant? C=120

b. What is the cost to remove 90% of the pollutant? C=300

c. What is the cost to remove 99% of the pollutant? C=3000

Question

d.	For what value is this equation undefined?

This is the question I  am trying to answer, so would it be 100%?

1.	The cost, in millions of dollars, to remove x % of pollution in a lake modeled by C=6000/200-2x 
a.	What is the cost to remove 75% of the pollutant? C=120
 
b.	What is the cost to remove 90% of the pollutant? C=300
 
c.	What is the cost to remove 99% of the pollutant? C=3000

hero · Answer

What the....? Again?

hero · Answer

The answer for d is $$x \ne 100$$

nannie · Answer

FOR WHAT VALUE IS THIS EQUATION UNDEFINED?

hero · Answer

I give up

hero · Answer

I told you several times

nannie · Answer

THANK YOU THAT IS WHAT I NEEDED

nannie · Answer

I'M SORRY , WASN'T SURE. I AM MATH ILLITERATE.