Return on total assets-hagerman corporation

Question

Problem: Hagerman Corporation reports the following items of the year 2011:

Sales (all on account)                 $200,000
Cost of Goods Sold                      120,000
Sales and Administrative Expense   40,000
Interest Expense                            10,000

Hagerman's income tax rate is 30%. The beginning balance of total assets was $140,000 and the ending balance was $90,000. The return on total assets was what number? Why?