When does the string first look completely flat for t > 0?

The pulse of Problem 9 travels to the right on a string whose ends at x = 0 and x = 4.0 m are both fixed in place. Imagine a reflected pulse that begins to move onto the string at an endpoint at the same time the incident pulse reaches that endpoint. The superposition of the incident and reflected pulses gives the shape of the string.

Data in Problem 9

(a) What is the position of the peak of the pulse shown in the figure at t = 3.00 s? 

(b) When does the peak of the pulse arrive at x = 4.00 m?

(cm) t=0 10 1 2 3 x (m) (cm) t= 0.20 s 10 5 1 3 x (m) 2.