The dissociation constant of acetic is x × 10–5. When 25 mL of 0.2 M CH₃COONa solution is mixed with 25 mL of 0.02 M CH₃COOH solution, the pH of the resultant solution is found to be equal to 5. The value of x is _______.
(a) 1
(b) 5
(c) 10
(d) 25