Finite Element solution to the 2nd Order Diff Equation with difussion and convection terms only

This function solves the following the following BVP using Galerkin method.

au'(x)+bu"(x)=0 for 0<=x<=d
BC: u(0)=0 and u(d)=h
Example:
Finding an approximate solution to the following BVP using 16 elements of equal length.
u'(x)-u"(x)=0 : 0<=x<=1
BC: u(0)=0 and u(1)=1
Solution:
>> Galerkin(16,1,-1,1,1)
The result includes the plots as shown in the screenshot and the displacement and error matrix.