Answer:
The answer is 17.5%
Step-by-step explanation:
Using Accounting Rate of Return (ARR)
ARR= Average Annual Accounting Profit/Average Investment ×100%
ARR = 70,000/400,000× 100% = 17.5%
Average Accounting Profit ?
 $
Sales Revenue 250,000
Cash Operating Expenses (100,000)
Cash flow 150,000
Depreciation Charge (See working) 80,000 
Average Accounting Profit  70,000 
Average Investment cost =$400,000 (Since scrap value is nil)
Working 
Depreciation ( Using straight line method)
Annual charge =400,000/5 yrs = $ 80,000.
ARR is used to measure relative project profitability .It is relative simple to calculate and interpret by the management.
It however ignores time value of money which is one of its greatest limitation.