For Each of the Following Events, Which Ones Result in an Exchange

For each of the following events, which ones result in an exchange transaction for the O'Brien Company? $$\begin{array} { | l | l | } \hline\underline{\quad\quad} & \text { a. Purchased land for cash and a note payable } \\\hline \underline{\quad\quad} & \text { b. Agreed to purchase one million inventory parts from a new supplier } \\\hline \underline{\quad\quad}& \text { c. Paid the employees for the week } \\\hline\underline{\quad\quad}& \text { d. One of our shareholders sells her shares to a new investor } \\\hline \underline{\quad\quad}& \text { e. Received inventory from a supplier under the new contract } \\\hline \underline{\quad\quad}& \text { f. Entered into a contract with a new cleaning service } \\\hline\end{array}$$