$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
7.18
\begin{equation} \begin{gathered}\label{equation:relative-Kan-extension-existence} \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{C}}^{0} \ar [r]^-{F_0} \ar [d] & \operatorname{\mathcal{D}}\ar [d]^{U} \\ \operatorname{\mathcal{C}}\ar [r]^-{G} \ar@ {-->}[ur]^{F} & \operatorname{\mathcal{E}}} \end{gathered} \end{equation}