IRR

Could you please explain why we are using discount rate of 14% and 20% to calculate the IRR, while using 5% and 20% is incorrect because with using 5% and 20% the IRR is 18.0% which is incorrect; the answer is A.

An investment project has net present values as follows:
At a discount rate of 5% $69,700 positive
At a discount rate of 14% $16,000 positive
At a discount rate of 20% $10,500 negative

Using the above figures, what is the BEST approximation of the internal rate of return of the investment project?
A 17.6%
B 17.9%
C 18.0%
D 22.7%