Help with Math WordProblem

A 1000L Tank contains 50L of a 25% brine solution. You add x liters of a 75% brine solution to the ank.

a)Show that the concentration C, the proportion of brine to total solution, in the final mixture is:

C= (3x+50)/(4(x+50))

b)Determine the domain of the function based on the physical constraints of the problem. Explain your answer.

c) Graph the concentration function. As the tank is filled, what happens to the rate at which the concentration of brine is increasing? What percent does the concentration of brine appear to approach?