How to solve this PDE? (Pleaaaaaaaaaaaaase!!)

From: Nas (nasimusus_at_yahoo.com)
Date: 09/17/04 

Date: 17 Sep 2004 07:20:06 -0700

Hi every one.

I would like to find function A(x,t) by solving this PDE:

dA/dt=cosh(ax).dA/dx + b.cosh(ax).t

"a" and "b" are constants. Does anyone has any idea of how I should
deal with it?

Thanks
Nas