Trying to plot a 3D pdf evolution of output signal

hey all i am trying to plot a 3D pdf evolution. The plot is depend on equation 8.92. I have upload two new image leading up to the equation.

If you could edit your post to include an image of the entire page from the text containing the function you want to plot and possibly even several previous pages so that the complete derivation could be seen then it might be possible to translate this into Mathematica.

hey there i have already upload the pages leading to the equation.