The task is to display the graph of the Amplitude versus time and the displacement of velocity versus time. Displacement of velocity is the derivative of the coordinate. Isn’t it? And
??? is velocity ??? is Amplitude in plot.
And is it right plot? 
Yes, that is right, but maybe it is better if you didn’t enter the values of parameters manually, for example you calculate k, and just type k, without typing its value : 17.33…etc