Two Sinusoidal Waves Travel Along the Same String

Multiple Choice

Two sinusoidal waves travel along the same string.They have the same wavelength and frequency.Their amplitudes are y_m1 = 2.5 mm and y_m2 = 4.5 mm, and their phases are π/4 rad and π/2 rad, respectively.What are the amplitude and phase of the resultant wave?

A) cannot solve without knowing the wavelength
B) 5.1 mm, 0.51 rad
C) 5.1 mm, 0.79 rad
D) 6.5 mm, 1.3 rad
E) 7.0 mm, 1.3 rad