Write a function to represent the situation described below. A chemist adds x litres of 65 % alcohol to a 20 L solution of 45 % alcohol. Write a function C (::) to represent the concentration of the solution as a function of the volume added, x. The function is: C (a) = Va a sin (a) ? When x = 0, the concentration is: Number % When x = 20, the concentration is: Number % When x gets very large, the concentration gets very close to: Number