The function f(x) = x^2 – 4x +3 which is defined for all real values of x, and x ? k. 
(a) Find the greatest possible value of k. 
(b) Determine the range of f. 
(c) Find the inverse function f-1 and state its domain and range. 
(d) Sketch the graphs of y = f(x) and f-1(x).