Suppose you have a solution containing $30mM$ of $CH3\frac{C}{O}OH$ and $1\mathrm{.}2M$ of $CH3\frac{C}{O}O-$with a $pH$ of $3\mathrm{.}9.$ What is the $pK$ a of the buffer? $2\mathrm{.}35\mathrm{.}35\mathrm{.}52\mathrm{.}8$