The following data pertains to Timmins Company's operations last year:
Required:
a. Compute the company's average operating assets.
b. Compute the company's residual income for the year.

a. Return on investment = Margin × Turnover
20% = 5% × Turnover
Turnover = 20% ÷ 5% = 4
Turnover = Sales ÷ Average operating assets
4 = $800,000 ÷ Average operating assets
Average operating assets = $800,000 ÷ 4 = $200,000
b. Before the residual income can be computed, we must first compute the company's net operating income for the year:
Margin = Net operating income ÷ Sales
5% = Net operating income ÷ $800,000
Net operating income = 5% × $800,000 = $40,000