We have: 
Net Income = 2,400 
Beginning total assets = 30,500 
Ending total assets = 20,000 
Return on asset is net income divided by average total assets. 
Average total assets = ( beginning total assets + ending total assets)/2 
 = (30500 +20000)/2 
 = 25,250 
Return on asset = net income/ average total assets 
 = 2400 /25250 
 =9.50% 
Therefore, Return on asset would be 9.50%.