How to embed?

[vin]

OK here is my question.

I have a file that contains a definition of a function

#exmpl.py

def foo(x,y):
        return x+y


Now, I want to embed Python in a C program.  After calling Py_Initialize(): 
I can call  PyRun_SimpleString("import exmpl\n"); to import my function.  
Now suppose that in my C program I have statements

double X,Y, result_in_c;
X=5.5; Y=6.6;

How do I pass X and Y to foo and get the output from foo to result_in_c so 
that I can process this output further in my C program?

Thanks
Vin