Getting error as variable undefined

[kalyani0820@gmail.com]

Hi all,

I'm a beginner, I was trying to practice qtp with sample application "Mercury Tours" provided by HP. When I try to automate this application, it is giving following error:
Variable is undefined: 'cint(uf)+cint(df)'

Line (55): "If total=[cint(uf)+cint(df)] *cint(nop)+tax Then".

I have attached the script. Please help me.......... where did i go wrong?

Cheers
Kalyani