3 g of acetic acid is added to 250 ml of 0.1 M HCl, and the solution is made up to 500 ml. To 20 ml of this solution, 12 ml of 5 M NaOH is added. The pH of the solution is ________.
(a) 2.0
(b) 4.0
(c) 7.0
(d) 10.0