Consider the function below. f(x, y) = ln(x + y − 9) (a) Evaluate f(4, 6). (b) Evaluate f(e, 9). (c) Find the domain of f. x > 9 y > 9 x + y > 9 x + y − 9 > 1 x > 9, y > 9 (d) Find the range of f. (Enter your answer using interval notation.)