Three sinusoidal waves of the same frequency travel along a string in the positive direction of an

Question:

Three sinusoidal waves of the same frequency travel along a string in the positive direction of an x axis. Their amplitudes are y1, y1/2, and y1/3, and their phase constants are 0, π/2, and π, respectively. What are the
(a) Amplitude and
(b) Phase constant of the resultant wave?
(c) Plot the wave form of the resultant wave at t = 0, and discuss its behavior as / increases.