$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
7.5
\begin{equation} \begin{gathered}\label{equation:categorical-pullback-relative-limit} \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{E}}' \ar [r]^-{F} \ar [d]^{U'} & \operatorname{\mathcal{E}}\ar [d]^{U} \\ \operatorname{\mathcal{C}}' \ar [r] & \operatorname{\mathcal{C}}. } \end{gathered} \end{equation}