A jet plane flying at a constant velocity v at a height \[h=8\text{ }km\], is being tracked by a radar R located at O directly below the line of flight. If the angle \[\theta \] is decreasing at the rate of \[0.025\text{ }rad/s\], the velocity of the plane when \[\theta =\text{ }60{}^\circ \]is:

• A. 1440 km/h       
• B.        960 km/h
• C. 1920 km/h       
• D.        480 km/h