I can't seem to subtract a numerical solution and the analytical solution of a PDE, help

Hey, to all!

First post here and after searching the web for answers I thought I'll ask it here.

haven't used Maple for a long time so I'm quite new in it.

I've solved a PDE in a numeric and in a analytic way and I want to the find the difference between the results.

I've come up with this:

1.2.mw

Had few tries with a few commands but for no success.

I seem to be able to find the specific value of the analytical solution but not the numeric one although it is solved.

Also I can't subtract to find the difference.

I will appreciate help in any kind,

Thank you!