Beginner really needs help with Maxima's basic concepts

Hello,

I am working on the binomial model and my example is based on that but
really my question relates to Maxima's basic concepts.

Here is my example:

I have %Delta and p defined as follows:

*%Delta:(fu-fd)/(S0*u-S0*d); (1)*

*p:(exp(r*T)-d)/(u-d); (2)*

I need to have the following expression (3) simplified by replacing the
%Delta with the expression given above in (1) and expressed in terms of p as
defined above in (2)...

*f:S0*%Delta*(1-u*exp(-r*T))+fu*exp(-r*T); (3)*

...so that I would ideally get this:

*f:exp(-r*T)*(p*fu + (1-p) * fd); (4)*

Is this possible? Can someone please help?

Julien.