Answer:
This machine’s accounting rate of return is 13 %=
Explanation:
Accounting Rate of return: The accounting rate of return is also known as average rate of return in which the net income is proportionate to the average investment. 
In mathematically, 
Accounting rate of return = Net income ÷ Average investment
where, average investment = (Purchase cost + salvage value) ÷ 2
                                               = ($700,000 + $100,000) ÷ 2
                                               = $400,000
Now, apply the above formula
So the Accounting rate of return = $52,000 ÷ $400,000 = 13%
Hence, this machine’s accounting rate of return is 13 %