Answer:
12%
Explanation:
The internal rate of return is that return in which the net present value is zero which means the initial investment is equal to the present value of the yearly cash flows after considering the discounting factor
In mathematically,
Initial investment = Present value of the yearly cash flows after considering the discounting factor
which equals to
$109,332 = $36,000 × PVIFA for four years
So, PVIFA for four years would be
=  $109,332 ÷ $36,000
= 3.037
And, the 3.037 for four years is the rate of interest 12%