Determine whether the following statements are true and give an explanation or counterexample.

a. The value of lim_x→3 x² - 9/x - 3 does not exist.

b. The value of lim_x→a f(x) is always found by computing f(a).

c. The value of lim_x→a f(x) does not exist if f(a) is undefined.

d. lim_x→0 √x = 0.

e. lim_x→π/2 cot x = 0.