The two important chlorides of phosphorus $PC{l}_3$ and $PC{l}_5,$ both important in the production of other phosphorous compounds, coexist in equilibrium through the reaction

$PC{l}_3(g)+C{l}_2(g)PC{l}_5(g)$

At $250C,$ an equilibrium mixture in a $2\mathrm{.}50L$ flask contains $0\mathrm{.}105gPC{l}_5,0\mathrm{.}220gPC{l}_3,$ and $2\mathrm{.}12gC{l}_2.$ What is the value of the equilibrium constant $(K_c)$ at $250C?$

A$)26\mathrm{.}3$

B$)100\mathrm{.}8$

C$)0\mathrm{.}010$

D$)0\mathrm{.}325$

E$)50\mathrm{.}4$