Buffer solution help

400.0 mL of a 1.25 M buffer solution is buffered to a pH of 4.89. If its pKa is 5.15, what is the mass of the acid and conjugate base is used (answer in grams).
The molecular weight of the acid is 218 g/mol and the molecular weight of the conjugate base is 247 g/mol.

Thanks!

pH = pKa + log[A-/HA]

4.89 = 5.15 + log[A-/HA]

[A-]/[HA] = 0.545

[A-] = 0.545[HA]

The ratio is 0.515. The total molarity of the buffer solution is 1.25, so:

[A-] + [HA] = 1.25

0.545[HA] + [HA] = 1.25

[HA] = 0.809 M
[A-] = 0.545[HA] = 0.441 M

You know your molarities, now multiply by the volume to find the moles of each:

[HA] = 0.809 M * 400 mL = 324 mmoles = 0.324 moles HA
[A-] = 0.441 M * 400 mL = 176 mmoles = 0.176 moles A-

You know your moles, now multiply by molecular weight for the mass:

0.324 moles HA (218 g / mol) = 71 g HA used
0.176 moles A- (247 g / mol) = 44 g A- used