The displacement of a string is given by y (x,t) = 0.06 sin (2πx/3) cos (120πt) where x and y are in m and t in s. The length of the string is 1.5m and its mass is 3.0 x 10^{-2} kg

(a) It represents a progressive wave of frequency 60Hz.

(b) It represents a stationary wave of frequency 60Hz.

(c) It is the result of superposition of two waves of wavelength 3 m, frequency 60Hz each travelling with a speed of 180 m/s in opposite direction.

(d) Amplitude of this wave is constant.