Are these correct...Please help

Question

1. The cost, in millions of dollars, to remove x % of pollution in a lake modeled by
a. What is the cost to remove 75% of the pollutant?

C=6,000/(200-2X)
C=6,000/(200-2*.75))
C=6,000/(200-1.5)
C=6,000/198.5
C=30.23 Million for 75% removal.

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

C=6,000/(200-2*.9)
C=6,000/200-1.8)
C=6,000/198.2
C=30.27 Million for 90% removal.

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

C=6,000/(200-2*.99)
C=6,000/(200-1.98)
C=6,000/198.02
C=30.30 Million for 99% removal.

I need help with the last two.
d. For what value is this equation undefined?
e. Do the answers to sections a–d match your expectations? Why or why not?

Answer 1

I have the same question. For what value is this equation undefined?
and
Do the answers to sections a-d match your expectations? why or why not?
I'm confused on how to answer this. Please help anyone! Thank you!