Consider the problem faced by a summer camp recreation director who is trying to choose activities for a rainy day. Information about possible activities is given in the table below. Let Xi stand for the binary decision variable that indicates whether activity i (i = 1 ... 9) is chosen or not.

a) Write the constraint that would make sure that no more than 2 computer activities can be done.

b) Write the constraint that would make sure that if basketball is chosen, then the music activity must be chosen.

c) Write the constraint such that "Painting" and "Drawing" cannot be chosen together.

\begin{tabular}{|l|l|} \hline Category & Activity \\ \hline Art & 1 - Painting \\ \hline Art & 2- Drawing \\ \hline Art & 3 - Nature Craft \\ \hline Music & 4 - Rhythm band \\ \hline Sports & 5 - Relay races \\ \hline Sports & 6 - Basketball \\ \hline Computer & 7 - Internet \\ \hline Computer & 8 - Creative writing \\ \hline Computer & 9 - Games \\ \hline \end{tabular}