4.

a. Margin = Net operating income ÷ Sales = $609,840 ÷ $10,890,000 = 5.6% b. Turnover = Sales ÷ Average operating assets = $10,890,000 ÷ $3,000,000 = 3.6 c. ROI = Net operating income ÷ Average operating assets = $609,840 ÷ $3,000,000 = 20.3% d. Residual income = Net operating income - Minimum required rate of return × Average operating assets = $609,840 - 16% × $3,000,000 = $129,840