Please provide formulas and explanations, thanks.

\begin{tabular}{|c|c|c|c|} \hline & Company A & Company B & Company C \\ \hline Sales... & $1,080,000 & $1,440,000 & $320,000 \\ \hline Operating income.... & $90,000 & & \\ \hline Average capital assets. & & $240,000 & $80,000 \\ \hline Return on investment (ROI)... & 25% & 25% & \\ \hline \multicolumn{4}{|l|}{ Minimum required rate of return: } \\ \hline Percentage.... & & & \\ \hline Dollar amount & $86,400 & $36,000 & $13,600 \\ \hline Residual income.... & & & ($5,600) \\ \hline \end{tabular}