A buffer is made up of 0.300 L of each of 0.500 M KH2PO4 and 0.317 M K2HPO4. Assuming that volumes are additive, (a.) calculate the pH of the buffer after the addition of 0.0500 mol of HCl to 0.600 L of buffer and (b.) the pH of the buffer after the addition of 0.0500 lol of NaOH to 0.600 L of the buffer. (pKa=7.21)