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\begin{document}

\title[101 Homework \#26]{Math 101: Algebra I \\ Homework, Day \#26}
\date{Assigned Tuesday, 25 October 2016; due Wednesday, 26 October 2016}

\maketitle

\vspace{1ex}

\begin{problab}{JV26.A} 
Show that a group is a category with one object in which all morphisms are isomorphisms.
\end{problab}

\begin{problab}{JV26.B} 
Let $\mathcal{C}$ be a category and let $A$ be a fixed object in $\mathcal{C}$.  Define a category $\mathcal{C}_A$ whose objects are arrows $f:Z \to A$ in $\mathcal{C}$.  What are the morphisms in $\mathcal{C}_A$?  Draw a diagram illustrating associativity of the composition law.
\end{problab}

\end{document}