B f ′ ¯ → D f ↑ ↑ g ′ A → g C {\displaystyle {\begin{aligned}B&{\bar {f'}}\rightarrow &D\\f{\Bigg \uparrow }&&{\Bigg \uparrow }&g'\\A&{\xrightarrow[{g}]{}}&C\end{aligned}}}