$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
3.46
\begin{equation} \label{diagram:pushout-lemma} \begin{gathered} \xymatrix@R =50pt@C=50pt{ \operatorname{Fun}(A,X) & \operatorname{Fun}(B,X) \ar [l]_{u} \\ \operatorname{Fun}(A',X) \ar [u] & \operatorname{Fun}(B',X), \ar [l]_{u'} \ar [u] } \end{gathered} \end{equation}