Compute the Dollar Amount of the Items Indicated by Letters

Compute the dollar amount of the items indicated by letters a through f in the table below.
$\begin{array}{|l|r|c|}\hline&\text { Case 1 } & \text { Case } 2\\\hline\\\hline \text { Sales } & \$ 5,500 & \$ 13,000 \\\hline \text { Beginning Merchandise Inventory } & 75 & \text { d } \\\hline \text { Net Cost of Purchases } & 4,975 & 4,600 \\\hline \text { Ending Merchandise Inventory } & \text { a } & 600 \\\hline \text { Cost of Goods Sold } & \text { b } & \text { e } \\\hline \text { Gross Margin } & \text { c } & 4,800 \\\hline \text { Operating Expenses } & 450 & \text { f } \\\hline \text { Income Before Income Taxes } & 150 & 1,200\\\hline\end{array}$