Are these correct...Please help

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?

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!

a. The cost to remove 75% of the pollutant is calculated by substituting 0.75 for x in the equation 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

Your calculation for removing 75% of the pollutant is correct.

b. To find the cost to remove 90% of the pollutant, use the same process:

C = 6,000/(200-2*.9)
C = 6,000/(200-1.8)
C = 6,000/198.2
C ≈ 30.27 Million

Your calculation for removing 90% of the pollutant is correct.

c. To calculate 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

Your calculation for removing 99% of the pollutant is correct.

d. To find the value for which the equation is undefined, set the denominator equal to zero and solve for x:

200-2X = 0
2X = 200
X = 100

Therefore, when x = 100, the equation is undefined.

e. Based on the calculations, the answers to sections a-d match the expected results. The cost to remove the pollutant decreases as the percentage of pollutant removal increases. This is expected since removing a larger portion of the pollutant should decrease the remaining cost.