A tank is filled with 100 L of a 40% alcohol solution (by volume). You repeatedly perform the following operation: Remove 2 L of the solution from the tank and replace them with 2 L of 10% alcohol solution.

a. Let C_n be the concentration of the solution in the tank after the nth replacement, where C₀ = 40%. Write the first five terms of the sequence {C_n}.

b. After how many replacements does the alcohol concentration reach 15%?

c. Determine the limiting (steady-state) concentration of the solution that is approached after many replacements.