The PK_a of Acetic Acid, HC₂H₃O₂, Is 4

The pK_a of acetic acid, HC₂H₃O₂, is 4.76. A buffer solution was made using an unspecified amount of acetic acid and 0.30 moles of NaC₂H₃O₂ in enough water to make 2.00 liters of solution. Its pH was measured as 4.40. How many moles of HC₂H₃O₂ were used?Hint: The opposite operation of log(x) is 10^x.

A) 0.13 mol
B) 0.18 mol
C) 0.60 mol
D) 0.69 mol
E) 1.37 mol