Answer:
6.83%
Explanation:
The computation of the accounting rate of return is shown below:
As we know that
Average accounting rate of return = Average annual operating income ÷ Initial Investment
where, 
Average annual operating income is 
Year 1 net cash inflow           $320,000
Year 2 net cash inflow          $280,000
Years 3-10 ($230,000 × 8)    $1,840,000
Total net cash flows                $2,440,000
Less: Total depreciation      ($1,450,000)
                                               $990,000
Divided it by years of life         ÷ 10  years 
Average annual operating income $99,000
So, 
Average accounting rate of return is 
 = $99,000 ÷ $1,450,000
= 6.83%