Answer:
the net present value is $606.64
Step-by-step explanation:
The computation of the net present value is shown below:
But before that the present value of annual cash inflows is to be determined i.e. 
Present value = annual cash flows × PVIFA(8%,4years) 
 = $8,400 × 3.3121 
 = $27,821.64 
 Now 
Net present value = Present value of cash flows - initial investment 
 = $27,821.64 - $27,215 
 = $606.64
Hence, the net present value is $606.64