Two sinusoidal waves, identical except for phase, travel in the same direction along a string and interfere to produce a resultant wave given by y(x,t)=(2.5 mm)sin(26.0x -4.0 s-1 * t+0.400 rad), with x in meters and t in seconds. 1.) What is the wavelength of the two waves (m)? [I already solved this] 2.) What is the phase difference between them (radians, so enter no unit)? 3.) What is their amplitude (mm)? Please HELP on #2 and #3!!!