A transverse wave traveling in a string in the -x direction has a period of 12.56 s. The tension of the string is 24.0 N and a 4.0 m piece of the string has a mass of 240 g. It is observed that any point on the string oscillates between +80 cm and -80 cm in the y-direction. Assuming the phase constant to be zero, write out the wave function of the wave. Find the transverse speed of a point on the string at x = 2.0 m at time t - 4s.