4. Consider the function 5x - 2 for x 5. At which values of x is f(x) not continuous? (a) f(x) is continuous at every real value of x. b) f(x) is discontinuous at x = 2 and x = 5 only. (c) f(x) is discontinuous at x = 2 only. (d) f(x) is discontinuous at x = 5 only