Integration with variables as constants

Hi,

I'm trying to integrate the following function with respect to r from 0 to inf:

         4  3 
      4 r  z 
  --------------- 
   3    / 2 r z \ 
  a  exp| ----- | 
        \   a   /

My question: How can I get a numerical value (double) while leaving Z and a as just constants in variable form?

For example, something in the form of 0.566 Z/a where Z and a are kept as just variables but the rest is evaluated to a number?

Thanks

[Oleg Komarov]

Do you have symbolic toolbox?

[Alex]

Yes I do

Answer 1

[Andrew Newell]

If your symbolic expression is y, you can use

yInt = int(y,r,0,Inf);

EDIT: However, you may not get a clear answer. I don't have the Symbolic Toolbox, but in Maple I have to specify that a>0 and z>0 before it gives me an algebraic expression.