A vessel contains $CO_2$ at $1000\;K$ temperature with pressure $0.5$ atm. Some of $CO_2$ is converted in to CO on addition of graphite . If total pressure at equilibrium is $0.8$ atm the value of $K_p$ is

Question

$\begin{array}{1 1} (a)\;3\;atm \\(b)\;0.3\;atm\\ (c)\;0.18\;atm \\ (d)\;1.8\;atm \end{array}$