\begin{tabbing}
$\vdash$  \=$\forall$$A$, $B$, $C$:Type, $g$:($A$$\rightarrow$($B$ + Top)), $f$:($B$$\rightarrow$($C$ + Top)), $x$:$A$.\+
\\[0ex]can{-}apply($f$ o $g$  ;$x$) $\sim$ (can{-}apply($g$;$x$) $\wedge_{b}$ can{-}apply($f$;do{-}apply($g$;$x$)))
\-
\end{tabbing}