NEED HELP ON PURCHASE 1 ( FINDING THE UNITS (PAIRS) IN ENDING INVENTORY STEP BY STEP PLEASE HELP!!!!

A sneaker uses FIFO for its inventory valuation, calculate the cost of ending inventory and cost of goods sold if ending inventory is 25 pairs. \begin{tabular}{|l|r|r|r|r|} \hline \multicolumn{1}{|c|}{ Beginning inventory and purchases } & Units (pairs) & Cost per pair & \multicolumn{1}{c|}{ Total cost } & \begin{tabular}{c} Units (pairs) in \\ ending inventory \end{tabular} \\ \hline Beginning inventory & 11 & $45.20 & $497.20 & 11 \\ \hline Purchase 1 & 21 & $40.20 & $844.20 & $953.80 \\ \hline Purchase 2 & 25 & $50.20 & & \\ \hline Ending inventory & 19 & & & \\ \hline \end{tabular} Required: Please use the above information to answer the following: Note: Use cells A4 to D10 from the given information to complete this question. \begin{tabular}{l|r|r|} \hline & Units (pairs) & \multicolumn{1}{|c|}{ Costs } \\ \hline Beginning inventory & 11 & $497.20 \\ \hline Purchases & 40 & $1,798.00 \\ \hline Goods available for sale & & $2,295.20 \\ \hline Ending inventory & 25 & \\ \hline Cost of goods sold & 26 & \\ \hline \end{tabular} Formula may only include cell references (no values)