Answer
$\rm Perfectly\; destructive.$
Work Step by Step
First of all, we need to sketch the problem as seen below.
We need to find what kind of interference is at point $\rm P$.
We know that the two waves are in phase, so their wavelength is the same and is given by
$$v=\lambda f$$
$$\lambda=\dfrac{v}{f}\tag 1$$
And we know that the phase difference at some point is given by
$$\Delta \phi=\dfrac{2\pi\Delta r}{\lambda}+\phi_0$$
where $\Delta r=r_2-r_1$ while $r_2=\sqrt{4^2+2^2}$
If the phase difference was an intger number of lambda, then the interference is perfectly constructive. And if is was some number of wavelengths and a half, then it is perfectly destructive.
Plugging the known;
$$\Delta \phi=\dfrac{2\pi(\sqrt{4^2+2^2}-4)}{\lambda}+0$$
Plugging from (1);
$$\Delta \phi=\dfrac{2\pi(\sqrt{4^2+2^2}-4)f}{v}=\dfrac{2\pi(\sqrt{4^2+2^2}-4)(1800)}{340}$$
$$\Delta \phi\approx 2.5(2\pi)\;\rm rad$$
So it is perfectly destructive.
