Two points are located at a distance of 10 m and 15 m from the source of oscillation. The period of oscillation is 0.05 s and the velocity of the wave is 300 m/s. What is the phase difference between the oscillations of two points?

(a) $\frac{\pi }{3}$

(b) $\frac{2\pi }{3}$

(c) $\pi$

(d) $\frac{\pi }{6}$